Subclasses of keystoneauth1.adapter.Adapter, such as openstacksdk's
openstack.proxy.Proxy [1], would like to be able to obtain configuration
from oslo_config conf options.
This commit splits the conf processing logic out of
keystoneauth1.loading.adapter.Adapter.load_from_conf_options (aka
keystoneauth1.loading.load_adapter_from_conf_options) into a helper
method, keystoneauth1.loading.adapter.process_conf_options.
This is a straight refactor, so no test changes are necessary.
[1] 16f2dbe3b0/openstack/proxy.py (L113)
Change-Id: I250c431ccf3883901f7dce151bc5011ac305f829