New approach attempts to be more accurate by measuring
the elapsed time by iteration. Also:
* Use a 10 seconds default timeout and a half a second
polling step. New values should better match the tuning
process on real-life scenarios.
* Correct elapsed_time computation.
* Add _retry_ioctl() to avoid bailing out on temporary
ioctl EINTR failures (no need to check for EAGAIN cause
we are opening the frontend on blocking mode)
* Small corrections to fail condition handling
56933d97ec