Clean up test_admin_password_rbac

Currently, test_admin_password_rbac uses deprecated functionality
that is removed by this commit. This commit specifically:
  - Removes pointless skip check
  - Adds a waiter for server to become active after changing
    server password to avoid error being thrown in server
    deletion

Change-Id: I8997f4d323f4d0861163986947ff229ac839fb52
1 file changed