Fix update hang.

Don't check ssh keys of VM (attempting to update them) if we are
changing the state of the host (up/down) as there is a good chance
it will be down and will never return any keys.

Signed-off-by: Sandon Van Ness <sandon@inktank.com>
Added suggested comment.

Signed-off-by: Sandon Van Ness <sandon@redhat.com>
Merge pull request #322 from ceph/wip-fix-update-hang

Fix update hang.