cfm: Remove cfm_remote_mpid configuration.

cfm: Remove cfm_remote_mpid configuration.

According to the 802.1ag specification, users should be able to
configure the CFM module with a list of remote endpoints with which
the local endpoint should have connectivity.  Commit 93b8df3853
"cfm: Remove Maintenance_Point and Monitor tables." changed the
behavior so that only one remote endpoint could be specified.  This
commit takes it further, by disallowing specification of any
remote endpoints.

Due to this change, the semantics of the fault flag are slightly
different.  Before, a fault was triggered if any of the configured
remote endpoints were unreachable (or with RDI), or if any
unconfigured remote endpoints were reachable.  Now a fault is
triggered if no remote endpoints are reachable at all, or if
reachable endpoints have set their RDI.

Bug #7014.