[c-nsp] MPLS x-connect to router itself

[Rubens Kuhl]

I was wondering if IOS MPLS routers (ME6500 PFC3C in my case) can
establish an MPLS x-connect to itself, although it's not the IP
address of router-id but another loopback address added for this
purpose.

The idea here is to avoid converting the port to switchport (MUX-UNI
allow switchport and MPLS x-connects but not routed interfaces and
switchport on the same physical interface) and to use the "backup
peer" resource so if the loopback interface have been shutdown to
force fail-over the router would then connect to another PE to deliver
the circuit.

Lab is currently in use by another scenario, and it would also not
tell me whether this is an IOS or platform limitation.

Rubens