Make clusters a required on start/stop cli
Make clusters a required on start/stop cli

Previously we would assume not specifying a cluster meant you want to
act on every cluster. This is a bit risky because a user could forget to
specify a cluster and end up start/stopping in production by accident.

Yelp/paasta,somic/paasta,gstarnberger/paasta,gstarnberger/paasta,somic/paasta,Yelp/paasta