If libapparmor-devel happens to be installed when building the
RPM, it will failed due to unlisted virt-aa-helper in %files.
Add support for apparmor in the spec, so that we can explicitly
turn it on/off, defaulting to off in all distros. This causes
--without-apparmor to be given to configure, preventing the
build failures if the user happens to have libapparmor-devel
present.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>