fix: ensure buffered events are sent in order

Before this commit, an event sent in the "connect" handler could be
sent before the events that were buffered while disconnected.

Related: socketio/socket.io-client#1458

Backported from 4885e7d

Author: darrachequesne

src/main/java/io/socket/client/Socket.java

@@ -386,8 +386,8 @@ private void onack(Packet<JSONArray> packet) {
 
     private void onconnect() {
         this.connected = true;
-        this.emit(EVENT_CONNECT);
         this.emitBuffered();
+        super.emit(EVENT_CONNECT);
     }
 
     private void emitBuffered() {

src/test/java/io/socket/client/SocketTest.java

@@ -233,4 +233,34 @@ public void call(Object... args) {
 
         socket.disconnect();
     }
+
+    @Test(timeout = TIMEOUT)
+    public void shouldEmitEventsInOrder() throws InterruptedException, URISyntaxException {
+        final BlockingQueue<String> values = new LinkedBlockingQueue<>();
+
+        socket = client();
+
+        socket.on(Socket.EVENT_CONNECT, new Emitter.Listener() {
+            @Override
+            public void call(Object... objects) {
+                socket.emit("ack", "second", new Ack() {
+                    @Override
+                    public void call(Object... args) {
+                        values.offer((String) args[0]);
+                    }
+                });
+            }
+        });
+
+        socket.emit("ack", "first", new Ack() {
+            @Override
+            public void call(Object... args) {
+                values.offer((String) args[0]);
+            }
+        });
+
+        socket.connect();
+        assertThat(values.take(), is("first"));
+        assertThat(values.take(), is("second"));
+    }
 }