Drop the MysqlClusterUniquePart validation
Drop the MysqlClusterUniquePart validation

Trying to use overcloud-without-mergepy currently fails with
a validation error around MysqlClusterUniquePart. This
works around the issue by temporarily dropping the validation.

Change-Id: If93945a2c3396b07b592d08efb1f66e11d6194dd
Partial-bug: #1405446

openstack/tripleo-heat-templates,trozet/tripleo-heat-templates,trozet/tripleo-heat-templates,trozet/opnfv-tht,trozet/opnfv-tht,rdo-management/tripleo-heat-templates,trozet/opnfv-tht,bcrochet/tripleo-heat-templates,rdo-management/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,bcrochet/tripleo-heat-templates,bcrochet/tripleo-heat-templates,dprince/tripleo-heat-templates,wyg3958/tripleo-heat-templates,wyg3958/tripleo-heat-templates