Fix conversion of {sec,nsec} to msec in timedwait on Windows

Internally time stamps and durations are all in nanoseconds, but the
platform abstraction uses {sec,nsec} (essentially a struct timespec) and
Windows uses milliseconds.  The conversion to milliseconds with upwards
rounding was broken, adding ~1s to each timeout.  In most of the handful
of uses the effect is minor in practice, but it does matter a lot in the
scheduling of Heartbeat and AckNack messages, e.g., by causing a simple
throughput test to exhibit periodic drops in throughput.

Signed-off-by: Erik Boasson <eb@ilities.com>

src/os/src/windows/os_platform_sync.c

@@ -97,7 +97,7 @@ os_result os_condTimedWait(os_cond *cond, os_mutex *mutex, const os_time *time)
     assert(cond != NULL);
     assert(mutex != NULL);
 
-    timems = time->tv_sec * 1000 + (time->tv_nsec + 999999999) / 1000000;
+    timems = time->tv_sec * 1000 + (time->tv_nsec + 999999) / 1000000;
     if (SleepConditionVariableSRW(&cond->cond, &mutex->lock, timems, 0)) {
         return os_resultSuccess;
     } else if (GetLastError() != ERROR_TIMEOUT) {