igt_require_gem() checks whether we can use the i915 fd for submitting
requests by detecting a wedged driver. It was intended to be used just
after opening DRIVER_INTEL for a gem test to provide an early skip if
the device was unusable. However, it is also used at the start of
library functions like igt_spin_batch_new() which may be called after
the test has setup some state, and importantly submitted some batches.
igt_require_gem() has the risk of then waiting on those batches, unless
we tell it to use a clean fd.

v2: Chase the /proc/self/fd/$fd link

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>