Cancel close timer after task execution

[RustedBones]

Fixes #140

When WebSocket.disconnec(closeCode, reason, closeDelay) is called and the close frame is not received from the server, the CloseTask fires.

However, in this case, no cancelCloseTask is called, leading to leave the thread from the close timer waiting for a new task.

Solution: If CloseTask fires, cancel the timer since it is used for a one time scheduling only.

As stated in the [Timer](https://docs.oracle.com/javase/7/docs/api/java/util/Timer.html#cancel()) Javadoc, it is safe to cancel within the task

[RustedBones]

staled project. closing PR