VOL-585: mandatory_operations assignment missing from class decl

Change-Id: I986c82633931ec5d5e222cf25042e5e87bfba5dc
(cherry picked from commit eada0c94d6eeab6e79098af53fc256a1feade597)
diff --git a/voltha/extensions/omci/omci_entities.py b/voltha/extensions/omci/omci_entities.py
index c5afd81..2f6b053 100644
--- a/voltha/extensions/omci/omci_entities.py
+++ b/voltha/extensions/omci/omci_entities.py
@@ -522,7 +522,7 @@
         ECA(ByteField("gal_loopback_configuration", None),
             {AA.R, AA.W}),
     ]
-    mandatory_operations = {}  # TODO
+    mandatory_operations = {OP.Create, OP.Delete, OP.Get, OP.Set}
 
 
 class GemPortNetworkCtp(EntityClass):