Disable request_id absence warning

Glare prints warnings into logs when request_id is
not specified in user context. But when the service
is used outside of OpenStack it's normal behavior
and logs confuse operators.

So, it's better to remove this warning and prevent
logs clogging with such warnings.

Change-Id: Ia588d5a2f067ae1333284b2def9b6612bc493cea

glare/api/middleware/context.py

@@ -70,9 +70,6 @@ class BaseContextMiddleware(base_middleware.ConfigurableMiddleware):
     def process_response(resp, request=None):
         try:
             request_id = resp.request.context.request_id
-        except AttributeError:
-            LOG.warning('Unable to retrieve request id from context')
-        else:
             # For python 3 compatibility need to use bytes type
             prefix = b'req-' if isinstance(request_id, bytes) else 'req-'
 
@@ -80,6 +77,8 @@ class BaseContextMiddleware(base_middleware.ConfigurableMiddleware):
                 request_id = prefix + request_id
 
             resp.headers['x-openstack-request-id'] = request_id
+        except AttributeError:
+            pass
 
         return resp