* added inform callback missing parameter

[gobixm]

pysnmp expects inform callback to have snmpEngine as first parameter.

[Lostboi]

Hey @gobixm i´ve merged your pull request here.

Sadly we dont know what happened to @etingof, but we try to maintain the project as far as we could.

So if you use the snmplabs docu of the snmpsim too, look forward here.