Remove "Arguments dropped when creating context" logging

This log was previously reduced from warning to debug.
Cinder removed it entirely in:
https://bugs.launchpad.net/cinder/+bug/1329156

The root cause is this:
Agent heartbeats use an admin context. The context is serialized
with its to_dict method, which exposes 'tenant' and 'project_name'
(These are properties of the class that are calculated from other
attributes). In the controller, this dict is used to initialize a
ContextBase, which does not accept tenant and project_name as arguments,
de facto sending those values as key word arguments.

We can either handle 'tenant' and 'project_name' specially, fix
it any other way, or drop the logging entirely. Is this logging
ever useful?

Change-Id: Ifd51b62bae7b96de44f04836015d2ed939bcb650
Closes-Bug: #1255441

neutron/context.py

@@ -73,10 +73,6 @@ class ContextBase(oslo_context.RequestContext):
             admin_roles = policy.get_admin_roles()
             if admin_roles:
                 self.roles = list(set(self.roles) | set(admin_roles))
-        # Log only once the context has been configured to prevent
-        # format errors.
-        if kwargs:
-            LOG.debug('Arguments dropped when creating context: %s', kwargs)
 
     @property
     def project_id(self):

neutron/tests/unit/test_neutron_context.py

@@ -41,11 +41,6 @@ class TestNeutronContext(base.BaseTestCase):
         self.assertIsNone(ctx.tenant_name)
         self.assertIsNone(ctx.auth_token)
 
-    def test_neutron_context_create_logs_unknown_kwarg(self):
-        with mock.patch.object(context.LOG, 'debug') as mock_log:
-            context.Context('user_id', 'tenant_id', foo=None)
-        self.assertEqual(mock_log.call_count, 1)
-
     def test_neutron_context_create_with_name(self):
         ctx = context.Context('user_id', 'tenant_id',
                               tenant_name='tenant_name', user_name='user_name')