Merge pull request phpredis#616 from linfangrong/patch-1

Update redis_cluster.c

Author: michael-grunder

redis_cluster.c

@@ -1600,6 +1600,7 @@ static void generic_zrange_cmd(INTERNAL_FUNCTION_PARAMETERS, char *kw,
                                zrange_cb fun)
 {
     redisCluster *c = GET_CONTEXT();
+    c->readonly = CLUSTER_IS_ATOMIC(c);
     cluster_cb cb;
     char *cmd; int cmd_len; short slot;
     int withscores=0;