1)boot the guest with "-rtc base=utc,clock=host" when host 100%
load (only linux)
2)boot the guest with "-rtc base=localtime,clock=host" when host
100% load (only windows)
3)reboot a guest with "-rtc base=localtime,clock=host" when host
100% load (only windows)
Signed-off-by: Nyama <yama@redhat.com>