Fix ZFS permissions bug with user namespaces
Fix ZFS permissions bug with user namespaces

Fix root directory of the mountpoint being owned by real root. This is
unique to ZFS because of the way file mountpoints are created using the
ZFS tooling, and the remapping that happens at layer unpack doesn't
impact this root (already created) holding directory for the layer.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)

aditirajagopal/docker,aditirajagopal/docker,aditirajagopal/docker