Assert that objects' lru pointer is correct

src/fellow_cache.c

@@ -3150,6 +3150,7 @@ fellow_cache_lru_work(struct worker *wrk, struct fellow_cache_lru *lru)
 			continue;
 		fco = fcs->fco;
 		AN(fco);
+		assert(fco->lru == lru);
 		r = pthread_mutex_trylock(&fco->mtx);
 		if (r != 0) {
 			assert(r == EBUSY);