Return `application/json` for image/load API (quite=1)

This fix tries to address the issue raised in 25529 wehre the
image/load API returns `application/json` for quiet=0 and
`text/plain` for quite=1.

This fix makes the change so that `application/json` is returned
for both quiet=0 and quite=1.

This fix has been tested manually.

This fix fixes 25529.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

api/server/router/image/image_routes.go

@@ -201,17 +201,14 @@ func (s *imageRouter) postImagesLoad(ctx context.Context, w http.ResponseWriter,
 	}
 	quiet := httputils.BoolValueOrDefault(r, "quiet", true)
 
-	if !quiet {
-		w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Content-Type", "application/json")
 
-		output := ioutils.NewWriteFlusher(w)
-		defer output.Close()
-		if err := s.backend.LoadImage(r.Body, output, quiet); err != nil {
-			output.Write(streamformatter.NewJSONStreamFormatter().FormatError(err))
-		}
-		return nil
+	output := ioutils.NewWriteFlusher(w)
+	defer output.Close()
+	if err := s.backend.LoadImage(r.Body, output, quiet); err != nil {
+		output.Write(streamformatter.NewJSONStreamFormatter().FormatError(err))
 	}
-	return s.backend.LoadImage(r.Body, w, quiet)
+	return nil
 }
 
 func (s *imageRouter) deleteImages(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

image/tarexport/load.go

@@ -30,8 +30,8 @@ func (l *tarexporter) Load(inTar io.ReadCloser, outStream io.Writer, quiet bool)
 	)
 	if !quiet {
 		progressOutput = sf.NewProgressOutput(outStream, false)
-		outStream = &streamformatter.StdoutFormatter{Writer: outStream, StreamFormatter: streamformatter.NewJSONStreamFormatter()}
 	}
+	outStream = &streamformatter.StdoutFormatter{Writer: outStream, StreamFormatter: streamformatter.NewJSONStreamFormatter()}
 
 	tmpDir, err := ioutil.TempDir("", "docker-import-")
 	if err != nil {