Skip nuke and just destroy VPS if nuke is --unlock

If the machine is being unlocked after than we definitely want to
just destroy it. This way nukes will always suceed with --unlock
even if the guest is down or in a borked state.

Signed-off-by: Sandon Van Ness <sandon@inktank.com>
Merge pull request #315 from ceph/wip-8877

Skip nuke and just destroy VPS if nuke is --unlock