Changes

mgw: Update RTP local address on E1 endpoints too

E1 endpoints still have usually 1 RTP connection on it (they do
E1-slot<->RTP), so we still need to update the RTP addr+port binding
upon CRCX & MDCX on those endpoints.

This fixes a recent regression with setups with E1 BTS failing to
establish calls.

Fixes: b317b0056a4eb48763dfbcde2bd68632d3346843
Change-Id: I52e91cd2d9d4b64961b76bb0fecc82494ca0d7cb