Clean up codes and fix some minor issues

1. Remove unnecessary warning messages in kvm_write_guest_page_kvm() and so on;
2. Use kvm_x86_ops->tlb_flush() instead of kvm_mmu_flush_tlb() to make it
valid immediately;
3. All exit reasons but EPT_VIOLATION will cut a quantum;
4. Change the test pattern to rollback once every 99 commits;
5. Do a second memory commit for each commit regardless of its exit reason;

Now it works fine without the floating points but will results in errors
when calculating floating points.

Signed-off-by: Le Tan <tamlokveer@gmail.com>