Automatic merge from submit-queue

Build and push kube-dns for 1.4 release.

Fix #31355.

Following docker images had been uploaded:
gcr.io/google_containers/kubedns-amd64:1.7
gcr.io/google_containers/kubedns-arm:1.7
gcr.io/google_containers/kubedns-arm64:1.7

Build for ppc64le is disabled by default, and it failed to be built using:
`KUBE_BUILD_PPC64LE=y make release`

I'm still working on making the ppc64le build. Updates will be added following this thread.

@girishkalele @thockin