Fix behavior when running dockerctl start --attach

--attach option skips check_ready steps, which would only
run after a container was killed. This led to unnecessary
checks that were run when the container is stopped. Now the
program exits quickly so supervisor can restart the container
as intended.

Additionally, consolidated cobbler checks so that it fails in
16 minutes intead of 32.

Change-Id: I4d3c6e20b8dec0d11af46080fe6941b6b34cae4a
Closes-Bug: #1393342
Merge "Fix behavior when running dockerctl start --attach"