Fix port parsing in check_via.

If a Via header contained an IPv6 address, we would not properly parse
the port. We would instead get the information after the first colon in
the address.

(closes issue #17614)
Reported by: oej
Patches: 
      diff uploaded by sperreault (license 252)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@275308 65c4cc65-6c06-0410-ace0-fbb531ad65f3