qemu.tests: new case to check guest clock with syscall

Signed-off-by: Xu Tian <xutian@redhat.com>
qemu.tests: add timedrift_check_clock_offset cfg

Signed-off-by: Xu Tian <xutian@redhat.com>
qemu.tests: add check clock offset when vm crash/bsod

Signed-off-by: Xu Tian <xutian@redhat.com>
qemu.tests: add check clock offset when guest bsod/crash

Signed-off-by: Xu Tian <xutian@redhat.com>