Fix integration-cli daemon restart with user namespaces enabled

The `d.root` dir is resolved to the full path to the graph dir after the
daemon starts, but on restart, should be set back to the parent (without
the "<uid>.<gid>" ending) so that it uses/resolves to the same graphdir
on restart.

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