zed: unclean disk attachment faults the vdev

If the attached disk already contains a vdev GUID, it
means the disk is not clean. In such a scenario, the
physical path would be a match that makes the disk
faulted when trying to online it. So, we would only
want to proceed if either GUID matches with the last
attached disk or the disk is in a clean state.

Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>