getMonoTime bug on mac (?)

[mratsim]

The change to the following time delay is seem to be guaranteed deadlock on Azure.

weave/weave/parallel_tasks.nim

Lines 262 to 270 in 4bb7916

	proc sleepingLion(stop_ms: int64): int64 =
	let start = getMonoTime()
	while true:
	let elapsed = inMilliseconds(getMonoTime() - start)
	if elapsed >= stop_ms:
	return elapsed
	dummy_cpt()

I suspect a getMonoTime bug on Mac in Nim.

Impact: need to change my test yet again.

[mratsim]

Race condition on my test that manifested on patforms withslow pthread_create, see #128 (comment)