When the mount code was refactored for Labels it was not correctly
updated to check whether policy supported mediation of the mount
class.  This causes a regression when the kernel feature set is
reported as supporting mount and policy is pinned to a feature set
that does not support mount mediation.

BugLink: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=882697#41
Fixes: 2ea3ffb7 ("apparmor: add mount mediation")
Reported-by: NFabian Grünbichler <f.gruenbichler@proxmox.com>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: NJohn Johansen <john.johansen@canonical.com>