Bug Fix: Some benchmark will cause reboot

Everythin is OK if we check every vmexit. I think the reason is that if we don't check some exits,
vcpu will execute some unreasonable instructions and cause shutdown and reboot.

Since ept violation and pause instruction consumes more than 99% vmexits, we check all the other
exits except these two.

Signed-off-by: Chunqi Li
OPTIMIZATION: Check commit when a vmexit is close to preemption timeout

Doesn't have much speed up. WTF!

Signed-off-by: Chunqi Li