openonuAdapterGo: MIB Template unknown ME

Create a test which checks the correct handling of an unknown ME in openonu go adapter.

Following is in ETCD MIB template expected:

"UnknownItuG988ManagedEntity": {
   "37": {
            "1": {
                   "AttributeMask": "8000",
                   "AttributeBytes": "0025000180000102030405060708090a0b0c0d0e0f101112131415161718191a"
                    }
             }
{color:#242424}}