This removes a level of indirection for the timer callback handling.
It also ensures we just have a single timeout message queued.

Also drops the 16bit MAX duration limit, as CreateTimerQueueTimer
uses a DWORD for the DueTime parameter, which is always UINT32.

CreateTimerQueueTimer already sets the period to 0, which makes it
a one-shot timer, but there is also the WT_EXECUTEONLYONCE, which
enforces the Period parameter to be 0.

Change-Id: I549142394334bdc098f053b42f222b23cf4fcecd