give an uniform check for release process bugfix

pkg/tiller/release_rollback.go

@@ -61,7 +61,7 @@ func (s *ReleaseServer) RollbackRelease(c ctx.Context, req *services.RollbackRel
 func (s *ReleaseServer) prepareRollback(req *services.RollbackReleaseRequest) (*release.Release, *release.Release, error) {
 	if err := validateReleaseName(req.Name); err != nil {
 		s.Log("prepareRollback: Release name is invalid: %s", req.Name)
-		return nil, err
+		return nil, nil, err
 	}
 
 	if req.Version < 0 {

pkg/tiller/release_testing.go

@@ -27,7 +27,7 @@ func (s *ReleaseServer) RunReleaseTest(req *services.TestReleaseRequest, stream
 
 	if err := validateReleaseName(req.Name); err != nil {
 		s.Log("releaseTest: Release name is invalid: %s", req.Name)
-		return nil, err
+		return err
 	}
 
 	// finds the non-deleted release with the given name