containerimage: fix possible race on parallel image create

When image was (externally or in parallel build request) created
in between Update and Create calls, Create can fail.

Handle this case by running Update again.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

Author: tonistiigi

exporter/containerimage/export.go

@@ -298,14 +298,20 @@ func (e *imageExporterInstance) Export(ctx context.Context, src *exporter.Source
 				}
 				for _, sfx := range sfx {
 					img.Name = targetName + sfx
-					if _, err := e.opt.Images.Update(imageClientCtx, img); err != nil {
-						if !errors.Is(err, cerrdefs.ErrNotFound) {
-							return nil, nil, nil, tagDone(err)
-						}
+					for { // handle possible race between Update and Create
+						if _, err := e.opt.Images.Update(imageClientCtx, img); err != nil {
+							if !errors.Is(err, cerrdefs.ErrNotFound) {
+								return nil, nil, nil, tagDone(err)
+							}
 
-						if _, err := e.opt.Images.Create(imageClientCtx, img); err != nil {
-							return nil, nil, nil, tagDone(err)
+							if _, err := e.opt.Images.Create(imageClientCtx, img); err != nil {
+								if !errors.Is(err, cerrdefs.ErrAlreadyExists) {
+									return nil, nil, nil, tagDone(err)
+								}
+								continue
+							}
 						}
+						break
 					}
 				}
 				tagDone(nil)