[lxc-users] overlayfs error after upgrade to vivid

[KATOH Yasufumi]

>>> On Fri, 1 May 2015 10:15:41 +0000
    in message   "Re: [lxc-users] overlayfs error after upgrade to vivid"
                  Serge Hallyn-san wrote:

> D'oh.  Confirmed.  To work around this, please do

> sudo mkdir /var/lib/lxc/ro_nginx/olwork

> lxc should obvoiusly do this on its own.  I hadn't noticed because normally
> lxc-create does it, but you have a preexisting container.

Oh... I had not noticed too...

We should mkdir in overlayfs_mount() if it doesn't exist.