Try to wipe multipath devices by checking the UUID

Since RD_NO_MULTIPATH is now set by default, and multipath does
not work in dracut, we need to check ourselves whether a disk
selected for wiping appears more than once.

Do this by checking whether or not LVM UUIDs match, since they
should be identical on identical disks.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1053505
Change-Id: Idd6ef9142bf516030988e0f66ad9dee30f4fe503
Signed-off-by: Ryan Barry <rbarry@redhat.com>