Kolla_keystone_user ansible module was not fully
using shade due limitations of Ansible version prior 2.0.
This has changed and lower version than 2 are not supported.
This change migrate the module to fully make use of shade library.
Maintains idempotency and the same features it had.
Change-Id: Ic0d21736fa666836b85f50b659c756edc0982fdd