LCS: implement re-use of existing A-interface conn

Location Services brings a new scenario to OsmoBSC: the MSC may create an
A-interface conn for a subscriber without an lchan being established (N-CONNECT
from MSC to BSC, so far only for an incoming inter-BSC handover).

If an MS becomes active while an A-interface conn is already established,
associate with an existing conn.

Change-Id: I42290f519a419ed7e8dd02a5ed0a5261b30a51e6
3 files changed