Use Go canonical import paths

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

Fixes #29014

pkg/controller/route/doc.go

@@ -16,4 +16,4 @@ limitations under the License.
 
 // Package route contains code for syncing cloud routing rules with
 // the list of registered nodes.
-package route
+package route // import "k8s.io/kubernetes/pkg/controller/route"