[AGENT++] How to disable engine id discovery mode in Agent++

[Pham, My V. (Mission Systems)]

Hello, 

I was trying to disable the engine id discovery mode in agent++ by using

,,,
v3MP *v3mp = new v3MP(engineId, snmpEngineBoots, stat);
v3mp->get_usm()->unset_discovery_mode();
...

Yet I was still able to send an SNMP request with some bogus engine ID
to the agent and get the request processed.  Obviously the engine ID
discovery is still enabled.  Please advise what I should do to turn this
off?

Thanks, 
My