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/configmap/doc.go

@@ -17,4 +17,4 @@ limitations under the License.
 // Package configmap provides Registry interface
 // and its REST implementation for storing
 // ConfigMap API objects.
-package configmap
+package configmap // import "k8s.io/kubernetes/pkg/registry/configmap"