Fix for CHOWA bug #2795132

Fix for CHOWA bug #2795132
CHOWA behaves differently from regular clients in respect of acknowledgement
of received messages. More in conferencing style.

It does not send 200 OK response to sent MESSAGE, but
returns 202 Accepted with 'message-id' header. Then it sends message
delivery notification in form of (BE)NOTIFY, type application/ms-imdn+xml.

Yes, problem was with not found session, I believe too. Because session
can be found by Call-Id only in case of conference/multiparty chat, not
simple two-party IM chat. In the latter case session is matched by
contact's URI.

Also fixed sending typing INFO messages before dialog is established. It
caused numerous '405 Method Not Allowed' errors in the provided log.