Glance RequestContext object doesn't retrieve user_domain attribute

[SFilatov]

Glance object does not retrieve domain attribute from request headers.
Glance policies use context to check rules so we are not able to use domains.

Context is formed in middleware _get_authenticated_context func:

kwargs = {
            'user': req.headers.get('X-User-Id'),
            'tenant': req.headers.get('X-Tenant-Id'),
            'roles': roles,
            'is_admin': CONF.admin_role.strip().lower() in roles,
            'auth_token': req.headers.get('X-Auth-Token', deprecated_token),
            'owner_is_tenant': CONF.owner_is_tenant,
            'service_catalog': service_catalog,
            'policy_enforcer': self.policy_enforcer,
            'request_id': request_id,
        }
return glance.context.RequestContext(**kwargs)