Do not lock vms when downburst fails.

Invalid os-type formerly threw KeyErrors and silently locked vms.
Other invalid os-type and invalid os-version permutations would print
error messages, lock a vms, and report that vms as being locked.

In all these cases, the vms created was unusable.

This new version does not lock in all these cases, and prints
appropriate log.info messages.  Code was also added to avoid confusing
messages as well.

Fixes: 8712
Signed-off-by: Warren Usui <warren.usui@inktank.com>