Add generic keystone cleanup mechanism

We should delete all created by benchmark resources:
"users", "roles", "services", "tenants" after benchmark execution.

We decide to use specific template in names.
(all names starts with "rally_k_" so we are able easy to check was
this resource created by benchmark or not).

blueprint keystone-benchmark

Change-Id: If5372138410a160c693314ebf0e728efd2682814
Merge "Add generic keystone cleanup mechanism"