undercloud: enable only metadata cleaning
undercloud: enable only metadata cleaning

We plan on disabling automated cleaning by default, but when it's
enabled, we only need the metadata cleaning, because the full secure
cleaning takes hours when secure ATA erase is not supported.

Partial-Bug: #1754609
Change-Id: Icd8b86a7ab3cff21efb113cb58bd6690cd29a03c

dprince/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,openstack/tripleo-heat-templates