AST-2018-005: Fix tdata leaks when calling pjsip_endpt_send_response(2)

AST-2018-005: Fix tdata leaks when calling pjsip_endpt_send_response(2)

pjsip_distributor:
   authenticate() creates a tdata and uses it to send a challenge or
   failure response.  When pjsip_endpt_send_response2() succeeds, it
   automatically decrements the tdata ref count but when it fails, it
   doesn't.  Since we weren't checking for a return status, we weren't
   decrementing the count ourselves on error and were therefore leaking
   tdatas.

res_pjsip_session:
   session_reinvite_on_rx_request wasn't decrementing the ref count
   if an error happened while sending a 491 response.
   pre_session_setup wasn't decrementing the ref count if
   while sending an error after a pjsip_inv_verify_request failure.

res_pjsip:
   ast_sip_send_response wasn't decrementing the ref count on error.

ASTERISK-27618
Reported By: Sandro Gauci

Change-Id: Iab33a6c7b6fba96148ed465b690ba8534ac961bf