Fix dbExpand not dividing by slots, resulting in consuming slots time…

…s the dictExpand

We meant to divide it by the number of slots, otherwise it will do slots times
dictExpand, bug was introduced in redis#11695.

src/db.c

@@ -2195,9 +2195,17 @@ int expireIfNeeded(redisDb *db, robj *key, int flags) {
 int dbExpand(const redisDb *db, uint64_t db_size, dbKeyType keyType, int try_expand) {
     dict *d;
     if (server.cluster_enabled) {
+        /* We don't know exact number of keys that would fall into each slot, but we can
+         * approximate it, assuming even distribution, divide it by the number of slots. */
+        int slots = 0;
+        for (int i = 0; i < CLUSTER_SLOTS; i++) {
+            if (clusterNodeGetSlotBit(server.cluster->myself, i))
+                slots++;
+        }
+        if (slots > 0) db_size = db_size / slots;
+
         for (int i = 0; i < CLUSTER_SLOTS; i++) {
             if (clusterNodeGetSlotBit(server.cluster->myself, i)) {
-                /* We don't know exact number of keys that would fall into each slot, but we can approximate it, assuming even distribution. */ 
                 if (keyType == DB_MAIN) {
                     d = db->dict[i];
                 } else {