Make an error state

[arpit-saxena]

When an unexpected thing happens during deployment, the service should be put in an error state which can be manually stopped. We can't leave the state as Deploying since no operation would then be able to work on it.

Needed here:

DeployBot/src/controllers/deploy.go

Lines 88 to 93 in e75a8f8

	// There should be no error here, ever. Checking it to make sure
	// TODO: On error, set state to an "error" state which only stop should be able to modify
	tag, err1 = history.SetState(a.RepoURL, tag, state)
	for ; err1 != nil; tag, err1 = history.SetState(a.RepoURL, tag, state) {
	log.Errorf("setting state to %v failed - %v. Retrying...", state.Status, err1)
	}