Apply the new dictUnlink() where possible.

Optimizations suggested and originally implemented by @oranagra.
Re-applied by @antirez using the modified API.

src/dict.c

@@ -478,8 +478,9 @@ dictEntry *dictUnlink(dict *ht, const void *key) {
 }
 
 /* You need to call this function to really free the entry after a call
- * to dictUnlink(). */
+ * to dictUnlink(). It's safe to call this function with 'he' = NULL. */
 void dictFreeUnlinkedEntry(dict *d, dictEntry *he) {
+    if (he == NULL) return;
     dictFreeKey(d, he);
     dictFreeVal(d, he);
     zfree(he);

src/lazyfree.c

@@ -57,7 +57,7 @@ int dbAsyncDelete(redisDb *db, robj *key) {
     /* If the value is composed of a few allocations, to free in a lazy way
      * is actually just slower... So under a certain limit we just free
      * the object synchronously. */
-    dictEntry *de = dictFind(db->dict,key->ptr);
+    dictEntry *de = dictUnlink(db->dict,key->ptr);
     if (de) {
         robj *val = dictGetVal(de);
         size_t free_effort = lazyfreeGetFreeEffort(val);
@@ -73,7 +73,8 @@ int dbAsyncDelete(redisDb *db, robj *key) {
 
     /* Release the key-val pair, or just the key if we set the val
      * field to NULL in order to lazy free it later. */
-    if (dictDelete(db->dict,key->ptr) == DICT_OK) {
+    if (de) {
+        dictFreeUnlinkedEntry(db->dict,de);
         if (server.cluster_enabled) slotToKeyDel(key);
         return 1;
     } else {

src/t_zset.c

@@ -1387,7 +1387,7 @@ int zsetDel(robj *zobj, sds ele) {
         dictEntry *de;
         double score;
 
-        de = dictFind(zs->dict,ele);
+        de = dictUnlink(zs->dict,ele);
         if (de != NULL) {
             /* Get the score in order to delete from the skiplist later. */
             score = *(double*)dictGetVal(de);
@@ -1397,12 +1397,11 @@ int zsetDel(robj *zobj, sds ele) {
              * actually releases the SDS string representing the element,
              * which is shared between the skiplist and the hash table, so
              * we need to delete from the skiplist as the final step. */
-            int retval1 = dictDelete(zs->dict,ele);
+            dictFreeUnlinkedEntry(zs->dict,de);
 
             /* Delete from skiplist. */
-            int retval2 = zslDelete(zs->zsl,score,ele,NULL);
-
-            serverAssert(retval1 == DICT_OK && retval2);
+            int retval = zslDelete(zs->zsl,score,ele,NULL);
+            serverAssert(retval);
 
             if (htNeedsResize(zs->dict)) dictResize(zs->dict);
             return 1;