When creating a DRBD disk, Ganeti reserves minor numbers on a per-node
basis. In case of a failed disk creation, these reservations should be
released. During the name/uuid refactoring, the invocation of the
function that releases the minors was not updated, resulting in no
minors being released in case of a DRBD disk creation failure.
Ganeti's verification utilities catch this error and rightly complain.
This patch fixes the issue by providing the UUID and not the name.

Signed-off-by: Hrvoje Ribicic <riba@google.com>
Reviewed-by: Helga Velroyen <helgav@google.com>