Be more consistent with the return code for requests received from invalid domain.

When Asterisk receives an INVITE from an external domain when allowexternaldomains=no
send a 403 instead of a 404. This is consistent with Asterisk's behavior when receiving
a REGISTER in this situation.

(Closes issue ASTERISK-19601)
Reported by Matthew Jordan
Patches:
	ASTERISK-19601-no401.patch uploaded by Mark Michelson (License #5049)
........

Merged revisions 369302 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@369303 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -23459,8 +23459,6 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 				 */
 				/* Fall through */
 			case SIP_GET_DEST_EXTEN_NOT_FOUND:
-			case SIP_GET_DEST_REFUSED:
-			default:
 				{
 					char *decoded_exten = ast_strdupa(p->exten);
 					transmit_response_reliable(p, "404 Not Found", req);
@@ -23469,6 +23467,10 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 						" '%s' rejected because extension not found in context '%s'.\n",
 						S_OR(p->username, p->peername), ast_sockaddr_stringify(&p->recv), decoded_exten, p->context);
 				}
+				break;
+			case SIP_GET_DEST_REFUSED:
+			default:
+				transmit_response_reliable(p, "403 Forbidden", req);
 			} /* end switch */
 
 			p->invitestate = INV_COMPLETED;