Verify that if a context is active at the time it is closed, that it is
either persistent and preemptible (with hangcheck running) or it shall
be removed from execution.

Fixes: 9a40bddd ("drm/i915/gt: Expose heartbeat interval via sysfs")
Testcase: igt/gem_ctx_persistence/heartbeat-close
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <stable@vger.kernel.org> # v5.7+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200928221510.26044-3-chris@chris-wilson.co.uk
(cherry picked from commit d3bb2f9b)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>