Remove leftover of hieradata cleanup
Remove leftover of hieradata cleanup

The commit e2680bbf7eba8b40424083900d21ec285754c86f removed usage
of CephManilaClientKey in manila-backend-cephfs.yaml but it didn't
remove comments about the parameter.

Change-Id: I65c1ef66833109d10882981f4a4f5852ee31acf0

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