Fix gate failure due to recent oslo.policy release

This fixes unittest job failure seen in the gate, which is
cause by the new release of oslo.policy, more info can be
found here [0].

[0] http://lists.openstack.org/pipermail/openstack-dev/2018-July/132312.html

Change-Id: I1a1e6af09b291a1dbba45676147da23983e7fd95

ironic_inspector/test/unit/test_utils.py

@@ -61,6 +61,7 @@ class TestCheckAuth(base.BaseTest):
 
     def test_invalid(self):
         request = mock.Mock(headers={'X-Identity-Status': 'Invalid'})
+        request.context = context.RequestContext()
         self.assertRaises(utils.Error, utils.check_auth, request)
 
     def test_not_admin(self):