coredns: Upgrade to v1.2.2

Upstream Changes:

-   coredns v1.2.2 (https://github.com/coredns/coredns/releases/tag/v1.2.2)

NOTE:

-   coredns image for 1.2.0 and 1.2.1 had been removed from https://console.cloud.google.com/gcr/images/google-containers/GLOBAL/coredns