Otherwise the check will return false if securityfs was not mounted
by the container's configuration.  In the past we let that quietly
proceed, but unconfined.  Now that we restrict such container
starts, this caused lxc-test-apparmor to fail.
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Dwight Engen <dwight.engen@oracle.com>