chan_sip: Honor Session-Expires in 200OK response when it's a RE-INVITE when...

chan_sip: Honor Session-Expires in 200OK response when it's a RE-INVITE when asterisk is the refresher.

RFC 4028 Section 7.2
 "UACs MUST be prepared to receive a Session-Expires header field in a
 response, even if none were present in the request." 

What changed
  After ASTERISK-20787, inbound calls to asterisk with no Session-Expires in the INVITE are now are offered
  a Session-Expires (1800 asterisk default) in the response, with asterisk as the refresher.

Symptom:
  After 900 seconds (asterisk default refresher period 1800), asterisk RE-INVITEs the device, the device
   may respond with a much lower Session-Expires (180 in our case) value that it is now using.

  Asterisk ignores this response, as it's deemed both an INBOUND CALL, and a RE-INVITE.

  After 180 seconds the device times out and sends BYE (hangs up), asterisk is still working with the
  refresher period of 1800 as it ignored the 'Session Expires: 180' in the previous 200OK response.
 
Fix:
	handle_response_invite() when 200OK, remove check for outbound and reinvite.
  
(closes issue ASTERISK-21664)

Reported by: alecdavis
Tested by: alecdavis
alecdavis (license 585)

Review https://reviewboard.asterisk.org/r/2463/
........

Merged revisions 387312 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 387319 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@387327 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -23162,7 +23162,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
 		}
 		/* Check for Session-Timers related headers */
-		if (st_get_mode(p, 0) != SESSION_TIMER_MODE_REFUSE && p->outgoing_call == TRUE && !reinvite) {
+		if (st_get_mode(p, 0) != SESSION_TIMER_MODE_REFUSE) {
 			p_hdrval = (char*)sip_get_header(req, "Session-Expires");
 			if (!ast_strlen_zero(p_hdrval)) {
 				/* UAS supports Session-Timers */