Create a BSC<->MSC interface and use it for the BSC MSC IP and the
BSC NAT to reduce code duplication on handling reconnects to the MSC
and cleaning up the local state. The code is only partially tested
and will contain bugs. Currently both the BSC and the NAT will just
exit on connection loss and this way have the current behavior.
The latency of setting up of the TCP connection can be quite high,
it is better to connect in a non blocking way. This code is working
by setting the socket nonblocking and temporarily replacing the
bfd callback with the connect handling.
Once the OS has connected our socket we switch back to normal operation.