tests: Correctly mock out security groups in NeutronFixture

For our immediate purposes, this should always return something so we
modify the mock to do just that. That requires some modifications to
existing tests but is otherwise pretty simple. A future change will
address the TODO contained within to properly mock the neutron API.

Change-Id: Ibbee7fd11c1aa254e399d302adbae69126e98262
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

doc/api_samples/servers/v2.69/servers-details-resp.json

@@ -5,6 +5,11 @@
             "id": "b6b0410f-b65f-4473-855e-5d82a71759e0",
             "status": "UNKNOWN",
             "tenant_id": "6f70656e737461636b20342065766572",
+            "security_groups": [
+                {
+                    "name": "default"
+                }
+            ],
             "links": [
                 {
                     "href": "http://openstack.example.com/v2.1/6f70656e737461636b20342065766572/servers/b6b0410f-b65f-4473-855e-5d82a71759e0",
@@ -17,4 +22,4 @@
             ]
         }
     ]
-}
+}