Changes

m3ua: m3ua_gen_error_msg(): include Routing Context IE in cause Invalid Routing Context

As per RFC4666 3.8.1:
"""
The "Invalid Routing Context" error is sent if a message is received
from a peer with an invalid (unconfigured) Routing Context value.
For this error, the invalid Routing Context(s) MUST be included in
the Error message."
"""

Hence add the originating Routing Context IE so the error message can be
further identified.
For the same reason, also add the Diagnostic Information for the
specific cases in the switch statement, and make them more robust about
possible null pointer dereference.

Change-Id: If821109701e315d17f5334c680670ea6c7bce3bd

xua_asp_fsm: Include Routing Context IE in Err msg cuase Invalid Routing Context

As per RFC4666 3.8.1:
"""
For this error, the invalid Routing Context(s) MUST be included in
the Error message.
"""

Change-Id: Ia8bff16248967209d73cd6d5b54ac30fda283247

xua_as_fsm: Remove FIXME regarding queueing of msgs during state PENDING

Queueing of messags during T(r) (state PENDING) is already implemented,
see xua_as_fsm_pending() further below in the same file.

Change-Id: Ie572367493066039f7022250d94b815a4da5bd16