res_pjsip_transport_websocket: Attach the Websocket module on outgoing INVITEs.

In order to alter the Contact header on in-dialog requests and responses the
Websocket module must be attached on outgoing INVITEs. The Contact header is
modified so that the PJSIP transport layer can find and use the existing
Websocket connection based on the source IP address, port, and transport.

ASTERISK-24143 #close
Reported by: Aleksei Kulakov
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Merged revisions 421955 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 421956 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@421957 65c4cc65-6c06-0410-ace0-fbb531ad65f3