MINOR: lru: do not allocate useless memory in lru64_lookup

lru64_lookup function was added in a previous patch of mine. This one
just remove a useless memory allocation.
diff --git a/src/lru.c b/src/lru.c
index 4a46505..719fe07 100644
--- a/src/lru.c
+++ b/src/lru.c
@@ -39,15 +39,6 @@
 	struct eb64_node *node;
 	struct lru64 *elem;
 
-	if (!lru->spare) {
-		if (!lru->cache_size)
-			return NULL;
-		lru->spare = malloc(sizeof(*lru->spare));
-		if (!lru->spare)
-			return NULL;
-		lru->spare->domain = NULL;
-	}
-
 	node = __eb64_lookup(&lru->keys, key);
 	elem = container_of(node, typeof(*elem), node);
 	if (elem) {