Version 1.12.12 of libsofia-sip-ua no longer automatically generates a
contact header element from the local ip address and port. Specifying
the contact tag does not break operation with the existing
library (1.12.11), but allows for operation on a system with
freeswitch 1.10.4 or later installed, which is built against this new
version of libsofia-sip-ua.
Change-Id: I5c35c5a4bad2fbe76c22ac6d7ee37c832e0ba246