Support control connection status query for a particular MSC.

Add a new control command 'msc.N.connection_status' which can be used
to query the connection status of a particular MSC with number N.

Keep the old control command 'msc_connection_status', which always
queries MSC 0, for backwards compatibility.

Change-Id: Ibd41474a1be80e782b19ec337c856b5efc593fa8
Related: OS#2729
3 files changed