Use Go canonical import paths

Add canonical imports only in existing doc.go files.
https://golang.org/doc/go1.4#canonicalimports

Fixes #29014

pkg/registry/replicaset/doc.go

@@ -16,4 +16,4 @@ limitations under the License.
 
 // Package replicaset provides Registry interface and it's RESTStorage
 // implementation for storing ReplicaSet api objects.
-package replicaset
+package replicaset // import "k8s.io/kubernetes/pkg/registry/replicaset"