ips: use interruptible waits in ips-monitor

This is what I intended to do since:
  1) the driver handles variable waits just fine, and
  2) interruptible waits aren't reported as load in the load avg.

Reported-and-tested-by: Andreas Hartmann <andihartmann@freenet.de>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>