Strengthen association matching when we haven't seen the INIT/INIT-ACK.

The fact that the vtag matches the initiate tag doesn't mean much if both are 0
(uninitialized).

Also leave in some (commented-out) debug to make debugging this stuff easier
in the future.

Change-Id: Id007de8bf9d2d4e0bb18309ed3e2572fedda45f1
Reviewed-on: https://code.wireshark.org/review/5571
Reviewed-by: Jeff Morriss <jeff.morriss.ws@gmail.com>