rtpengine: fail the call when rtpengine replies with an error

Since the failover change (3d0959a), an error reply that is not a
failover error breaks out of the retry loop and is returned as a
success. So rtpengine_delete(), the recording, block, forward and
unsubscribe functions return true when rtpengine refused them, and
error_pv is never set for such errors.

Go to the error path instead, as before that change and as the async
path does.

(cherry picked from commit 9aa23bf)

Author: dragos-oancea

modules/rtpengine/rtpengine.c

@@ -2967,7 +2967,11 @@ static bencode_item_t *rtpe_function_call(bencode_buffer_t *bencbuf, struct sip_
 						else
 							continue; /* one more loop */
 					} else {
-						break; /* break the loop and exit with error */
+						/* not a failover error - fail the call */
+						RTPE_STOP_READ();
+						if (!error.len)
+							err = "proxy returned an error";
+						goto error;
 					}
 				}
 			} else {