api/server: explicitly ignore unhandled errors (errcheck)

```
api/server/router/build/build_routes.go:309:41: Error return value of `(*encoding/json.Decoder).Decode` is not checked (errcheck)
api/server/router/build/build_routes.go:431:11: Error return value of `io.Copy` is not checked (errcheck)
api/server/router/container/container_routes.go:582:13: Error return value of `conn.Write` is not checked (errcheck)
api/server/router/grpc/grpc_routes.go:38:12: Error return value of `conn.Write` is not checked (errcheck)
api/server/router/grpc/grpc_routes.go:39:12: Error return value of `resp.Write` is not checked (errcheck)
api/server/router/image/image_routes.go:94:15: Error return value of `output.Write` is not checked (errcheck)
api/server/router/image/image_routes.go:139:15: Error return value of `output.Write` is not checked (errcheck)
api/server/router/image/image_routes.go:164:15: Error return value of `output.Write` is not checked (errcheck)
api/server/router/image/image_routes.go:180:15: Error return value of `output.Write` is not checked (errcheck)
api/server/router/plugin/plugin_routes.go:126:15: Error return value of `output.Write` is not checked (errcheck)
api/server/router/plugin/plugin_routes.go:165:15: Error return value of `output.Write` is not checked (errcheck)
api/server/router/plugin/plugin_routes.go:273:15: Error return value of `output.Write` is not checked (errcheck)
```

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

api/server/router/build/build_routes.go

@@ -176,7 +176,7 @@ func (br *buildRouter) postPrune(ctx context.Context, w http.ResponseWriter, r *
 	if err := httputils.ParseForm(r); err != nil {
 		return err
 	}
-	filters, err := filters.FromJSON(r.Form.Get("filters"))
+	fltrs, err := filters.FromJSON(r.Form.Get("filters"))
 	if err != nil {
 		return errors.Wrap(err, "could not parse filters")
 	}
@@ -191,7 +191,7 @@ func (br *buildRouter) postPrune(ctx context.Context, w http.ResponseWriter, r *
 
 	opts := types.BuildCachePruneOptions{
 		All:         httputils.BoolValue(r, "all"),
-		Filters:     filters,
+		Filters:     fltrs,
 		KeepStorage: int64(ks),
 	}
 
@@ -234,12 +234,12 @@ func (br *buildRouter) postBuild(ctx context.Context, w http.ResponseWriter, r *
 	}
 
 	output := ioutils.NewWriteFlusher(ww)
-	defer output.Close()
+	defer func() { _ = output.Close() }()
 
 	errf := func(err error) error {
 
 		if httputils.BoolValue(r, "q") && notVerboseBuffer.Len() > 0 {
-			output.Write(notVerboseBuffer.Bytes())
+			_, _ = output.Write(notVerboseBuffer.Bytes())
 		}
 
 		// Do not write the error in the http output if it's still empty.
@@ -290,7 +290,7 @@ func (br *buildRouter) postBuild(ctx context.Context, w http.ResponseWriter, r *
 	// Everything worked so if -q was provided the output from the daemon
 	// should be just the image ID and we'll print that to stdout.
 	if buildOptions.SuppressOutput {
-		fmt.Fprintln(streamformatter.NewStdoutWriter(output), imgID)
+		_, _ = fmt.Fprintln(streamformatter.NewStdoutWriter(output), imgID)
 	}
 	return nil
 }
@@ -306,7 +306,7 @@ func getAuthConfigs(header http.Header) map[string]types.AuthConfig {
 	authConfigsJSON := base64.NewDecoder(base64.URLEncoding, strings.NewReader(authConfigsEncoded))
 	// Pulling an image does not error when no auth is provided so to remain
 	// consistent with the existing api decode errors are ignored
-	json.NewDecoder(authConfigsJSON).Decode(&authConfigs)
+	_ = json.NewDecoder(authConfigsJSON).Decode(&authConfigs)
 	return authConfigs
 }
 
@@ -428,7 +428,7 @@ func (w *wcf) notify() {
 	w.mu.Lock()
 	if !w.ready {
 		if w.buf.Len() > 0 {
-			io.Copy(w.Writer, w.buf)
+			_, _ = io.Copy(w.Writer, w.buf)
 		}
 		if w.flushed {
 			w.flusher.Flush()

api/server/router/image/image_routes.go

@@ -91,7 +91,7 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite
 		if !output.Flushed() {
 			return err
 		}
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 
 	return nil
@@ -136,7 +136,7 @@ func (s *imageRouter) postImagesPush(ctx context.Context, w http.ResponseWriter,
 		if !output.Flushed() {
 			return err
 		}
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 	return nil
 }
@@ -161,7 +161,7 @@ func (s *imageRouter) getImagesGet(ctx context.Context, w http.ResponseWriter, r
 		if !output.Flushed() {
 			return err
 		}
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 	return nil
 }
@@ -177,7 +177,7 @@ func (s *imageRouter) postImagesLoad(ctx context.Context, w http.ResponseWriter,
 	output := ioutils.NewWriteFlusher(w)
 	defer output.Close()
 	if err := s.backend.LoadImage(r.Body, output, quiet); err != nil {
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 	return nil
 }

api/server/router/plugin/plugin_routes.go

@@ -123,7 +123,7 @@ func (pr *pluginRouter) upgradePlugin(ctx context.Context, w http.ResponseWriter
 		if !output.Flushed() {
 			return err
 		}
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 
 	return nil
@@ -162,7 +162,7 @@ func (pr *pluginRouter) pullPlugin(ctx context.Context, w http.ResponseWriter, r
 		if !output.Flushed() {
 			return err
 		}
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 
 	return nil
@@ -270,7 +270,7 @@ func (pr *pluginRouter) pushPlugin(ctx context.Context, w http.ResponseWriter, r
 		if !output.Flushed() {
 			return err
 		}
-		output.Write(streamformatter.FormatError(err))
+		_, _ = output.Write(streamformatter.FormatError(err))
 	}
 	return nil
 }