Prevent outbound SIP NOTIFY packets from displaying a port of 0

Prevent outbound SIP NOTIFY packets from displaying a port of 0

In the change from 1.6.2 to 1.8, ast_sockaddr was introduced which changed the
behavior of ast_find_ourip such that port number was wiped out.  This caused
the port in internip (which is used for Contact and Call-ID on NOTIFYs) to be
0.  This change causes ast_find_ourip to be port-preserving again.

(closes issue ASTERISK-19430)
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Merged revisions 357665 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@357667 65c4cc65-6c06-0410-ace0-fbb531ad65f3