Fixed #1796: Avoid infinite registration loop caused by contact rewrite.



git-svn-id: http://svn.pjsip.org/repos/pjproject@4944 74dad513-b988-da41-8d7b-12977e46ad98
Misc (re #1782): In case if STUN server is configured and NAT-traversal is in process user can delete this server from setting list. In that case in internal_stun_resolve_cb we should check that STUN server is available. (Thanks to Max Bondarenko for the patch).



git-svn-id: http://svn.pjsip.org/repos/pjproject@4945 74dad513-b988-da41-8d7b-12977e46ad98