cmd/gitmirror: cleanups & more Kubernetes work

It's now running, but not hooked up the coordinator yet.

Updates golang/go#18817

Change-Id: I5870af1e0bfe5213886f7faeb138127986a7234c
Reviewed-on: https://go-review.googlesource.com/36801
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
4 files changed