No need to be passing ctx to update_lock()

... or update_keys() or scan_for_locks()

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Use new ssh_keyscan() function

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Rewrite ssh public key updating

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>