Removed admin_* from devstack config
Removed admin_* from devstack config

The admin_* variables are a relic of the Keystone V2 api and
should no longer be used at all.

It's important to keep the devstack config clean, as it is often
used as a reference for configuring services.

* Removed deprecated admin_user, admin_password and admin_tenant.

Story: 2004272
Task: 27821

Change-Id: I132e670f446e5172dc4f1847be7779645060ca4d

openstack/magnum,openstack/magnum,ArchiFleKs/magnum,ArchiFleKs/magnum