Use Go canonical import paths

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

Fixes #29014

pkg/util/jsonpath/doc.go

@@ -17,4 +17,4 @@ limitations under the License.
 // package jsonpath is a template engine using jsonpath syntax,
 // which can be seen at http://goessner.net/articles/JsonPath/.
 // In addition, it has {range} {end} function to iterate list and slice.
-package jsonpath
+package jsonpath // import "k8s.io/kubernetes/pkg/util/jsonpath"