[pkg-apparmor] Bug#879585: apparmor: Pin the AppArmor feature set in Stretch to Linux 4.9's

[intrigeri at debian.org]

Package: apparmor
Version: 2.11.0-3
Severity: important

This is about supporting Stretch users who have enabled AppArmor
and run a new kernel, e.g. from stretch-backports.

Similarly to #879584, let's pin the AppArmor feature set to the one
supported by the Stretch stock kernel, i.e. the one the AppArmor
policy shipped in Stretch works well with.

Cheers,
-- 
intrigeri