x/build: consistent, documented deployment strategies for all kube binaries

[adams-sarah]

there's no real, consistent or documented deployment approach for kube binaries.
not critical, but good to keep everything consistent. less divergence == happy maintainer.

let's modify Makefiles such that they adhere to the following pattern:

deploy-prod: push-prod
	kubectl set image deployment/$(BINARY_NAME)-deployment $(BINARY_NAME)=gcr.io/symbolic-datum-552/$(BINARY_NAME):$(VERSION)

this pattern already present in pubsubhelper, devapp.

ensure:
coordinator, gitmirror, gopherbot, maintner, scaleway, ... (did I miss any?)

[gopherbot]

Change https://golang.org/cl/61730 mentions this issue: all: normalize GKE configs/Makefiles to follow common patterns