CORD-1908: cleanup VSG service

Change-Id: Ib7fa0a68dbba185b30d7cd1ea1b425ad3d33a8d3
(cherry picked from commit 645c0c587527d68566d70d3bc8d39981c551a786)
diff --git a/xos/attic/vsgserviceinstance_model.py b/xos/attic/vsgserviceinstance_model.py
new file mode 100644
index 0000000..08ede12
--- /dev/null
+++ b/xos/attic/vsgserviceinstance_model.py
@@ -0,0 +1,29 @@
+
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+def __init__(self, *args, **kwargs):
+    super(VSGServiceInstance, self).__init__(*args, **kwargs)
+
+def __xos_save_base(self, *args, **kwargs):
+    if not self.creator:
+        if not getattr(self, "caller", None):
+            # caller must be set when creating a vCPE since it creates a slice
+            raise XOSProgrammingError("VSGServiceInstance's self.caller was not set")
+        self.creator = self.caller
+        if not self.creator:
+            raise XOSProgrammingError("VSGServiceInstance's self.creator was not set")
+
+    return False