fix: simplify passing auditLog eventType (#15278)

Rename Trigger -> Event to be a more appropriate
name for the audit event.

Bonus: fixes a bug in AddMRFWorker() it did not
cancel the waitgroup, leading to waitgroup leaks.

cmd/bucket-handlers.go

@@ -649,6 +649,7 @@ func (api objectAPIHandlers) DeleteMultipleObjectsHandler(w http.ResponseWriter,
 			dv := DeletedObjectReplicationInfo{
 				DeletedObject: dobj,
 				Bucket:        bucket,
+				EventType:     ReplicateIncomingDelete,
 			}
 			scheduleReplicationDelete(ctx, dv, objectAPI)
 		}