Updated openstack/openstack
Project: openstack-dev/devstack  01e5f721b47fa525a37041bfc92fe3caa4706f68

Pull dstat logic into its own function so grenade can use it

In order to use dstat on the new side of grenade, pull dstat code into
its own lib with the function start_dstat

Change-Id: I5c908d594a6f3a90ed4b3f744002bf606841cf07