Fixing an action cleanup bug.

After a failed action, we were recording the failure, but not
cleaning up the original action. And a test. Also some cleanup:
- added a 'vtctl ReadTabletAction command
- using it in tests to not wait random amounts of time
  (the added test time is less than the time gained!)
- also fixing parameter passing in tabletmanager.py test.
WaitForAction is not ZK specific.
Merge branch 'master' into replication
Merge branch 'master' of github.com:youtube/vitess