Delete ERROR+DELETING VMs during compute startup.

We should perhaps do this check during message bus reconnection as
well.. Anyhow, if a compute node is offline during a nova API call
to delete an instance, and the rabbit message is lost for some
reason (or alternatively if the delete method throws an error)
then the task state is not cleared and won't be cleared on compute
restart, leaving it wedged forever.

Change-Id: Ie0a47958eb0fb58307902437a95634d5f54f74f3
Fixes-bug: #1281324
Co-Authored-By: Steve Kowalik <steven@wedontsleep.org>