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>
Nothing appears to even use the return value of ```ssh_keyscan()``` here. Couldn't we just remove that whole block?