If aufs is already modprobe'd but we are in a user namespace, the
aufs driver will happily load but then get eperm when it actually tries
to do something. So detect that condition.
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Upstream-commit: 2a71f28a4e1167dee32aa16ddbc819c9d9e77f71
Component: engine