GTPv2_Emulation: routing improvements: Prioritize response, fallback to TEID

First try forwarding to component transmitting the originating request,
since this is the most fine-grained match.
Finally, if no specific match was found and if messages belongs to
TEID0, send it over that port as a fallback.

Fixes: 1d2cc67036e95a0c3ee3ac7738d7e15d5f76b8a2
Change-Id: Ie96d65085fb352489150183415dbd6cc8237a47c
1 file changed