chan_pjsip: Store transport info for outgoing channels

chan_pjsip: Store transport info for outgoing channels

Outgoing PJSIP channels did not have transport information stored in
their session datastore when CHANNEL(pjsip,local_addr) or
CHANNEL(pjsip,remote_addr) was read. As a result, the address fields
were empty on B-leg channels even though other dialog fields such as
call-id and URIs were available.

Store the selected local transport address and destination address for
outgoing UAC session requests once the request is transmitted and the
transport information is known.

Fixes: #871