[SNMP4J] Agent setup for V3 "set/get" requests and "inform" notifications

[Mark Gorokhov]

I'm setting up a V3 agent for "set/get" requests and "inform"
notifications for the same user.

Setting up an USM User by calling
   usm.addUser(
      user.getSecurityName(), 
      usm.getLocalEngineID(), 
      user);
works for "set/get" requests but fails for "inform" notifications.

Setting up an USM User by calling
   usm.addUser(
      user.getSecurityName(), 
      null, 
      user);
works for "inform" notifications but fails for "set/get" requests.

Attempt to add the same user twice with usm.getLocalEngineID() and
"null" returns error -1406 for get-request: invalid engine ID

How to overcome this conflict? Could be the same user object reused for
V3 "set/get" requests and "inform" notifications?

Thanks,
Mark G.