Feature: crm_mon --neg-location drbd-fence-by-handler

Adds a list of negative location constraints to crm_mon output,
optionally filtered by id prefix.

Example output:

<normal crm_mon output>
...

Fencing constraints:

drbd-fence-by-handler-iscsi-vmstore2-rule-ms_drbd_iscsi-vmstore2 prevents ms_drbd_iscsi-vmstore2 from running as master on bk13-2

If so configured (DRBD fencing-policy != dont-care, fence-peer handler
set to crm-fence-peer.sh), a DRBD Primary places these constraints when
the replication link is not established.

This condition is otherwise not obvious from crm_mon output,
as to pacemaker, everything looks "normal".