res_pjsip: Change log message from error to warning for valid use cases

If a SIP MESSAGE is triggered for an endpoint that is currently not registered
- and therefore has no valid contact associated - an error message was logged.
Since this is a valid request in a valid use cases this is now changed to a
warning, as discussed with Matt Fredrickson on the asterisk-dev mailing list.

Change-Id: I55eb62d2712818a58c7532119dec288bd98cf0c0

res/res_pjsip.c

@@ -3779,7 +3779,7 @@ static int create_out_of_dialog_request(const pjsip_method *method, struct ast_s
 			contact = ast_sip_location_retrieve_contact_from_aor_list(endpoint->aors);
 		}
 		if (!contact || ast_strlen_zero(contact->uri)) {
-			ast_log(LOG_ERROR, "Unable to retrieve contact for endpoint %s\n",
+			ast_log(LOG_WARNING, "Unable to retrieve contact for endpoint %s\n",
 					ast_sorcery_object_get_id(endpoint));
 			return -1;
 		}

res/res_pjsip_messaging.c

@@ -655,7 +655,7 @@ static int msg_send(void *data)
 	}
 
 	if (ast_sip_create_request("MESSAGE", NULL, endpoint, uri, NULL, &tdata)) {
-		ast_log(LOG_ERROR, "PJSIP MESSAGE - Could not create request\n");
+		ast_log(LOG_WARNING, "PJSIP MESSAGE - Could not create request\n");
 		return -1;
 	}