shared.cfg: Add config to timedrift_monotonicity for windows guest

"date +%s%N" cannot show the current time for windows guest.

Signed-off-by: Shuping Cui <scui@redhat.com>
Merge pull request #1364 from spcui/timedrift_monotonicity_fix

shared.cfg: Add config to timedrift_monotonicity for windows guest