The openstack/manila-image-elements repository has a specific
release job, legacy-manila-publishimage-generic. In order to
support release requests for manila-image-elements, we need
to create a specific release model ("manila-image-elements")
where that job is a valid release job. That will allow
manila-image-elements to drop direct tagging ACLs.
Change-Id: Ida32d45c1e5587b98eca5e4ed36880a77a92698e