Relax even more the identification of DRBD8 devices

This patch adds a new success condition for identifying DRBD8 devices:
if the local device is correct, but the network peer is not, we shutdown
the network and attach to the correct one (this also handles going to
standalone mode).

This new check (and its actions) is based on the fact that we don't pass
incorrect data from the master to the node (otherwise we could start
syncing with an incorrect peer.

Reviewed-by: imsnah