Fix typo in option group shortcut 'aGENT' in NEC plugin

Also adds a test to check if option group shortcuts work.

Fix bug #1183576

Change-Id: Ib2843f2b2b4e35964fb4bb5280fda8f5c9e2ba0c
Merge "Fix typo in option group shortcut 'aGENT' in NEC plugin"