HPCC-9056 Build break in thor (Windows)

Recent addition of call to Semaphore::init() breaks build in Windows.
Linux Signature is
	void reinit(unsigned initialCount=0U)
and Windows sig is
	void reinit(unsigned initialCount)
This fix changes Windows to default to 0 as well

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>