LibpodAPI.BuildImage: don't require a name for the new image

When we finish building an image, we try to look up its ID by looking up
the image using the name that we were asked to assign to the image.  If
we weren't asked to assign a name to the image, that would produce an
error.  The BuildImage() API we're using returns the image's ID anyway,
so we can skip the lookup and just return the ID directly.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

pkg/varlinkapi/images.go

@@ -143,6 +143,7 @@ func (i *LibpodAPI) GetImage(call iopodman.VarlinkCall, id string) error {
 func (i *LibpodAPI) BuildImage(call iopodman.VarlinkCall, config iopodman.BuildInfo) error {
 	var (
 		namespace []buildah.NamespaceOption
+		imageID   string
 		err       error
 	)
 
@@ -249,7 +250,8 @@ func (i *LibpodAPI) BuildImage(call iopodman.VarlinkCall, config iopodman.BuildI
 
 	c := make(chan error)
 	go func() {
-		_, _, err := i.Runtime.Build(getContext(), options, newPathDockerFiles...)
+		iid, _, err := i.Runtime.Build(getContext(), options, newPathDockerFiles...)
+		imageID = iid
 		c <- err
 		close(c)
 	}()
@@ -291,13 +293,9 @@ func (i *LibpodAPI) BuildImage(call iopodman.VarlinkCall, config iopodman.BuildI
 	}
 	call.Continues = false
 
-	newImage, err := i.Runtime.ImageRuntime().NewFromLocal(config.Output)
-	if err != nil {
-		return call.ReplyErrorOccurred(err.Error())
-	}
 	br := iopodman.MoreResponse{
 		Logs: log,
-		Id:   newImage.ID(),
+		Id:   imageID,
 	}
 	return call.ReplyBuildImage(br)
 }