gbproxy: Improve VTY state introspection

* allow to print not only BSS-side BVCs, but also SGSN-side
* differentiate between SIG and PTP BVC
* print the actual BVC FSM state name instead of just UNBLOCKED/nothing

Change-Id: I8e09a9dc296b15094d191b0451d04457c815d116
2 files changed