Recent fixes in the apparmor kernel code is now making at least the CI
environment and quite possibly some others fail due to an invalid path
in the pivot_root stanza.

So update both lines to allow a more generic pivot_root call for
anything in LXC's work directory.
Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>