mirror sleep : set sleep to SLICE_TIME/10 (10ms)

mirror sleep : set sleep to SLICE_TIME/10 (10ms)

Current make too much sleep because

if (now - last_pause_ns > SLICE_TIME) {
         last_pause_ns = now;
         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, SLICE_TIME);

so, we sleep SLICE_TIME, then at next iteration if lastpause("SLICE_TIME") > SLICE_TIME, we sleep again.
So, it almost always sleep at each iteration.

This patch set the sleep value to  SLICE_TIME/10.

I have benched it, I have very scanning speed without impacting vm performance.

Signed-off-by: Alexandre Derumier <aderumier@odiso.com>