Extra compute services_client API endpoints

This patch:
  - adds ``disable_log_reason`` and ``update_forced_down`` API
    endpoints to the compute ``services_client``
  - adds corresponding unit tests and schemas
    (for 2.11 microversion)
  - changes ``host_name`` parameter in the unit tests for
    ``services_client`` to ``host`` because ``host_name``
    is wrong; see [0] for example

However, this patch does not add API tests for these endpoints
because they result in compute services being forced down
or disabled, which are dangerous to test in the gates.

Valid use cases for these APIs include:
  - negative testing
  - RBAC testing (forcing a BadRequest but ensuring policy enforcement
    happens beforehand)

[0] https://developer.openstack.org/api-ref/compute/#update-forced-down

Change-Id: I641218e104bba55e3679a7111e7f3d042ad7665b
6 files changed