Use Go canonical import paths

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

Fixes #29014

pkg/kubelet/doc.go

@@ -16,4 +16,4 @@ limitations under the License.
 
 // Package kubelet is the package that contains the libraries that drive the Kubelet binary.
 // The kubelet is responsible for node level pod management.  It runs on each worker in the cluster.
-package kubelet
+package kubelet // import "k8s.io/kubernetes/pkg/kubelet"