core: added missing field in sip_msg_update_buffer

- added a missing field in sip_msg_update_buffer()
  when restoring message fiedls: msg->pid.

src/core/msg_translator.c

@@ -3276,6 +3276,7 @@ int sip_msg_update_buffer(sip_msg_t *msg, str *obuf)
 	/* restore msg fields */
 	msg->buf = tmp.buf;
 	msg->id = tmp.id;
+	msg->pid = tmp.pid;
 	msg->rcv = tmp.rcv;
 	msg->set_global_address = tmp.set_global_address;
 	msg->set_global_port = tmp.set_global_port;