python3: use monotonic clock for condvar if possible

python3: use monotonic clock for condvar if possible

The timeout for threading.Lock, threading.Condition, etc, is not using
a monotonic clock, it is affected if the system time (realtime clock)
is set.

This patch will make condvar use monotonic clock.
Refence: https://bugs.python.org/issue41710

Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>