fix v2 migration on add-drop devices

Migration to v2 (0002) was wrong. Our add/drop devices do not have an
interface named 'osc' but 'eth2' (unfortunately the physical ports on
those devices do not have those ports labeled).

Also, our network YANG models and velia code did not account for eth2
device. It was as it simply never existed...

Change-Id: Iae6a6cf8b9584bdc42af99e0a44dcba715583913
diff --git a/tests/czechlight-cfg-fs/data/v0_sdn-roadm-add-drop_empty/startup.json b/tests/czechlight-cfg-fs/data/v0_sdn-roadm-add-drop_empty/startup.json
new file mode 100644
index 0000000..2c63c08
--- /dev/null
+++ b/tests/czechlight-cfg-fs/data/v0_sdn-roadm-add-drop_empty/startup.json
@@ -0,0 +1,2 @@
+{
+}