The default autoresume delay is about 5 seconds. It's possible on a
system that's not very fast this might not be a long enough time, since
an asynchronous hotplug event we scheduled on the chamelium that was
intended to happen during suspend could happen before we actually manage
to suspend. So, add a function that allows us to increase the autoresume
time to ensure this never happens during suspend/resume tests with the
chamelium.

Cc: Tomeu Vizoso <tomeu@tomeuvizoso.net>
Signed-off-by: Lyude <lyude@redhat.com>

Changes since v1:
- Use igt_require, not assert