Use Go canonical import paths

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

Fixes #29014

contrib/mesos/pkg/hyperkube/doc.go

@@ -18,4 +18,4 @@ limitations under the License.
 // kubernetes-mesos components into a single binary form, providing a
 // simple mechanism for intra-component discovery as per the original
 // Kubernetes hyperkube package.
-package hyperkube
+package hyperkube // import "k8s.io/kubernetes/contrib/mesos/pkg/hyperkube"