This change refactors current implementation to determine key manager
backend for cinder and nova, based on the following two points.
- keymgr_api_class was deprecated a while ago. We can remove this
parameter now.
- We don't have to redefine the parameter in puppet-tripleo layer but
we can use the parameter implemented in puppet-nova or puppet-cinder
directly.
Change-Id: I265ac3762823ea8930cc43150dc7b317f337f709