security: Fix return types of .probe callbacks

security: Fix return types of .probe callbacks

The .probe member of virSecurityDriver struct is declared to
return virSecurityDriverStatus enum. But there are two instances
(AppArmorSecurityManagerProbe() and
virSecuritySELinuxDriverProbe()) where callbacks are defined to
return an integer. This is an undefined behavior because integer
has strictly bigger space of possible values than the enum.

Defined those aforementioned callbacks so that they return the
correct enum instead of int.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>