Ensure bo is set should we panic in VBO_DerefBusyObj

bin/varnishd/cache/cache_fetch.c

@@ -973,6 +973,6 @@ VBF_Fetch(struct worker *wrk, struct req *req, struct objcore *oc,
 		}
 	}
 	VSLb_ts_req(req, "Fetch", W_TIM_real(wrk));
-	THR_SetBusyobj(NULL);
 	VBO_DerefBusyObj(wrk, &bo);
+	THR_SetBusyobj(NULL);
 }

bin/varnishd/cache/cache_req_fsm.c

@@ -516,8 +516,8 @@ cnt_pipe(struct worker *wrk, struct req *req)
 
 	V1P_Process(req, bo);
 	http_Teardown(bo->bereq);
-	THR_SetBusyobj(NULL);
 	VBO_DerefBusyObj(wrk, &bo);
+	THR_SetBusyobj(NULL);
 	return (REQ_FSM_DONE);
 }