tools/set_device_owner: Work around udev bug in Fedora 12
tools/set_device_owner: Work around udev bug in Fedora 12

- Unblock all signals before running udev settle.  This fixes a udev
timeout on Fedora 12 which would prevent us from setting block device
permissions correctly.

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr