Implements caching around basic assignment CRUD actions.
* assignment_api.get_domain
* assignmnet_api.get_domain_by_name
* assignment_api.get_project
* assignment_api.get_project_by_name
* assignment_api.get_role
The Create, Update, and Delete actions for domains, projects and
roles will perform proper invalidations of the cached methods listed
above.
Specific Cache Layer Tests added around assignment CRUD.
Modifications of LDAP tests done to handle caching concepts.
List methods are not covered by this patchset (list_projects, list_domains,
list_roles).
Grants are not subject to caching in this patchset.
DocImpact
partial-blueprint: caching-layer-for-driver-calls
Change-Id: Ic4e1a2d93078e55649ce9410ebece9b4d09b095a
ead4f98e82