udev: Race fix- load and trigger dev rule

The rule file is generated, yet not synch-loaded in memory, so a VM with
a direct lun fails to start.
This patch reloads the rules before triggering using the new private
udev functions - udevReloadRules() in supervdsmServer.py .
Also added a check in appropriateDevice() (hsm.py) to make sure the
mapping is indeed there.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=891300
Change-Id: If3b2008a3d9df2dcaf54190721c2dd9764338627
Signed-off-by: Lee Yarwood <lyarwood@redhat.com>
Signed-off-by: Vered Volansky <vvolansk@redhat.com>
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/11410
Reviewed-by: Allon Mureinik <amureini@redhat.com>