freetdm: ftmod_zt - clear FTDM_CHANNEL_EVENT flag on zt_channel_next_event when set,

                    but retrieve event from channel even when it's not

libs/freetdm/src/ftmod/ftmod_zt/ftmod_zt.c

@@ -1006,6 +1006,8 @@ FIO_CHANNEL_NEXT_EVENT_FUNCTION(zt_channel_next_event)
 
 	if (ftdm_test_flag(ftdmchan, FTDM_CHANNEL_EVENT)) {
 		ftdm_clear_flag(ftdmchan, FTDM_CHANNEL_EVENT);
+	}
+
 	if (ioctl(ftdmchan->sockfd, codes.GETEVENT, &zt_event_id) == -1) {
 		ftdm_log_chan(ftdmchan, FTDM_LOG_ERROR, "Failed retrieving event from channel: %s\n",
 				strerror(errno));
@@ -1089,9 +1091,6 @@ FIO_CHANNEL_NEXT_EVENT_FUNCTION(zt_channel_next_event)
 	span->event_header.channel = ftdmchan;
 	*event = &span->event_header;
 	return FTDM_SUCCESS;
-	}
-
-	return FTDM_FAIL;
 }
 
 /**