Disable domain does not cascade

As gyee pointed out in a related review[1], disabling a domain does not
need to cascade to owned projects/users as the effect of disabling a
domain only needs to be enforced service-side when a user is requesting
auth.

[1]: https://review.openstack.org/#/c/19787/

Change-Id: Ibd9882bdb933381f26a9ac4daf7e78ddf5dc53b3
Merge "Disable domain does not cascade"