mgcp_trunk: remove audio_name and audio_payload

get rid of deprecated trunk parameters which seem to be leftovers
from the old osmo-bsc_mgcp implementation. This is in particular
audio_name and audio_payload in struct mgcp_trunk_config which
allowed the user to "hardcode" an andio name and payload type
via VTY configuration

The removal of the struct members above also require a change to
mgcp_codec.c. The code that is is never actively used and even
causes wrong behavior when activated (set the no-transcoding
flag in VTY). Since the code is removed also the unit tests
also require to be changed to match the new behavior.

Change-Id: Ia050ec3cd34b410dfe089c41b977ae3d5aed7354
Related: OS#2659
4 files changed