PJSIP: Add log messages when requests are received for non-existent endpoints

(closes issue ASTERISK-22552)
Reported by: Rusty Newton
Review: https://reviewboard.asterisk.org/r/2934/
........

Merged revisions 401938 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@401939 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_pjsip_endpoint_identifier_user.c

@@ -102,6 +102,8 @@ done:
 			return NULL;
 		}
 		ast_debug(3, "Retrieved endpoint %s\n", ast_sorcery_object_get_id(endpoint));
+	} else {
+		ast_debug(3, "Could not identify endpoint by username '%s'\n", endpoint_name);
 	}
 	return endpoint;
 }