Fix rootwrap behavior in folsom.2 bug:1130549

Folsom.2 changes rootwrap behavior, this adds
the new rootwrap.conf file, and adds the nova.conf
parameter needed to configure it.
It doesn't remove the rootwrap_helper parameter that
will go away in Folsom.3

Tracked with bug https://bugs.launchpad.net/openstack-cisco/+bug/1130549