devicemapper: remove unused _parseDevFile and getDevUuid

Change-Id: I5f491407aa59490c8828e865604470f60919aaf8
Signed-off-by: Yeela Kaplan <ykaplan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/14714
Reviewed-by: Dan Kenigsberg <danken@redhat.com>