res_pjsip_transport_websocket: Fix security events and simplify implementation.

Transport type determination for security events has been simplified to use
the type present on the message itself instead of searching through configured
transports to find the transport used.

The actual WebSocket transport has also been simplified. It now leverages the
existing PJSIP transport manager for finding the active WebSocket transport
for outgoing messages. This removes the need for res_pjsip_transport_websocket
to store a mapping itself.

(closes issue ASTERISK-22897)
Reported by: Max E. Reyes Vera J.

Review: https://reviewboard.asterisk.org/r/3036/ 
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Merged revisions 403256 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@403257 f38db490-d61c-443f-a65b-d21fe96a405b
res_pjsip_t38: Add the framehook to the channel only on first INVITE.

The check for determining whether the T.38 framehook should be added to
the channel or not has now been changed to guarantee adding only occurs
on the first incoming or outgoing INVITE.
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Merged revisions 403258 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@403259 f38db490-d61c-443f-a65b-d21fe96a405b