core: use the same test as upstart for apparmor

core: use the same test as upstart for apparmor

Lennart:
> Hmm, I just noticed this patch:
>
> https://code.launchpad.net/~mdeslaur/upstart/apparmor-support/+merge/164169
>
> It contains a different check for AppArmor. Basically something like this:
>
> /sys/module/apparmor/parameters/enabled == 'Y'
>
> I'd prefer if we could change our code to do the same, given that
> the Ubuntu guys are guys are upstream for apparmor.

https://bugs.freedesktop.org/show_bug.cgi?id=63312