Pass credentials to glance client.

The auth creds dict was created but not passed to the glance client,
causing the following tests to fail with 401 Unauthorized:

  CreateRegisterImagesTest.test_register_then_upload
  CreateRegisterImagesTest.test_register_with_invalid_data

Change-Id: Icca9632f5de66ee7e957116e8dc60b53de9c1c87
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 097cfb9..7f39118 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -11,6 +11,12 @@
 build_timeout=600
 catalog_type=compute
 
+[image]
+username=admin
+password=********
+tenant=admin
+auth_url=http://localhost:5000/v2.0
+
 [environment]
 image_ref=3
 image_ref_alt=4