Fix issue #73 double calls of clearTimeout()
Fix issue #73 double calls of clearTimeout()

Callback in `$request->whenComplete()` calls naked `clearTimeout()` without checking if the timer has been cleared already.

This may lead up to issue #73, and the swoole exception would interfere with subsequent promise fulfillment.

Using `delTimer()` instead of `clearTimeout()` would mitigate this issue.
hprose/hprose-php