Fix bug where the client is not present in server.clients when free'ing it

When creating the readable event results in an error (this happens when
the server hits OS limits), the client was not added to the list of
clients when freeClient was called. This results in an assertion error.
It is better to check this condition first and free the client
immediately when this condition occurs. Port of 00a90feb.

src/networking.c

@@ -17,6 +17,14 @@ redisClient *createClient(int fd) {
     anetNonBlock(NULL,fd);
     anetTcpNoDelay(NULL,fd);
     if (!c) return NULL;
+    if (aeCreateFileEvent(server.el,fd,AE_READABLE,
+        readQueryFromClient, c) == AE_ERR)
+    {
+        close(fd);
+        zfree(c);
+        return NULL;
+    }
+
     selectDb(c,0);
     c->fd = fd;
     c->querybuf = sdsempty();
@@ -43,11 +51,6 @@ redisClient *createClient(int fd) {
     c->pubsub_patterns = listCreate();
     listSetFreeMethod(c->pubsub_patterns,decrRefCount);
     listSetMatchMethod(c->pubsub_patterns,listMatchObjects);
-    if (aeCreateFileEvent(server.el, c->fd, AE_READABLE,
-        readQueryFromClient, c) == AE_ERR) {
-        freeClient(c);
-        return NULL;
-    }
     listAddNodeTail(server.clients,c);
     initClientMultiState(c);
     return c;