builder/dockerfile: remove containerManager.removeContainer()

This was just a very thin wrapper for backend.ContainerRm(), and the
error it returned was not handled, so moving this code inline.

Moving it inline also allows differentiating the error message to
distinguish the "removing all intermediate containers" from "removing container"
(when cancelling a build).

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

builder/dockerfile/containerbackend.go

@@ -62,7 +62,10 @@ func (c *containerManager) Run(ctx context.Context, cID string, stdout, stderr i
 		case <-ctx.Done():
 			log.G(ctx).Debugln("Build cancelled, killing and removing container:", cID)
 			c.backend.ContainerKill(cID, "")
-			c.removeContainer(cID, stdout)
+			err = c.backend.ContainerRm(cID, &backend.ContainerRmConfig{ForceRemove: true, RemoveVolume: true})
+			if err != nil {
+				_, _ = fmt.Fprintf(stdout, "Removing container %s: %v\n", stringid.TruncateID(cID), err)
+			}
 			cancelErrCh <- errCancelled
 		case <-finished:
 			cancelErrCh <- nil
@@ -122,22 +125,11 @@ func (e *statusCodeError) StatusCode() int {
 	return e.code
 }
 
-func (c *containerManager) removeContainer(containerID string, stdout io.Writer) error {
-	rmConfig := &backend.ContainerRmConfig{
-		ForceRemove:  true,
-		RemoveVolume: true,
-	}
-	if err := c.backend.ContainerRm(containerID, rmConfig); err != nil {
-		fmt.Fprintf(stdout, "Error removing intermediate container %s: %v\n", stringid.TruncateID(containerID), err)
-		return err
-	}
-	return nil
-}
-
 // RemoveAll containers managed by this container manager
 func (c *containerManager) RemoveAll(stdout io.Writer) {
 	for containerID := range c.tmpContainers {
-		if err := c.removeContainer(containerID, stdout); err != nil {
+		if err := c.backend.ContainerRm(containerID, &backend.ContainerRmConfig{ForceRemove: true, RemoveVolume: true}); err != nil {
+			_, _ = fmt.Fprintf(stdout, "Removing intermediate container %s: %v\n", stringid.TruncateID(containerID), err)
 			return
 		}
 		delete(c.tmpContainers, containerID)