Better identify deprecated configuration options
Better identify deprecated configuration options

If a configuration option is tagged as deprecated in the code and the
help text does not start with DEPRECATED: add this to better identify
options that are no longer used.

If the code provides an additional deprecated reason, append this to
the provided help text of the configuration option.

Change-Id: I1a7c76c0109a6e59cc87d0ddc942c6d1cfb9dc91

openstack/openstack-doc-tools,openstack/openstack-doc-tools