improve manager disconnection and cleanup

Author: nkzawa

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

@@ -490,15 +490,22 @@ private void cleanup() {
         On.Handle sub;
         while ((sub = this.subs.poll()) != null) sub.destroy();
 
+        this.packetBuffer.clear();
+        this.encoding = false;
         this.lastPing = null;
+
+        this.decoder.destroy();
     }
 
     /*package*/ void close() {
+        logger.fine("disconnect");
+        this.skipReconnect = true;
+        this.reconnecting = false;
         if (this.readyState != ReadyState.OPEN) {
+            // `onclose` will not fire because
+            // an open event never happened
             this.cleanup();
         }
-        this.skipReconnect = true;
-        this.reconnecting = false;
         this.backoff.reset();
         this.readyState = ReadyState.CLOSED;
         if (this.engine != null) {
@@ -507,7 +514,7 @@ private void cleanup() {
     }
 
     private void onclose(String reason) {
-        logger.fine("close");
+        logger.fine("onclose");
         this.cleanup();
         this.backoff.reset();
         this.readyState = ReadyState.CLOSED;