* Create a 'devstack/upgrade/resources.sh' file to be used by
Grenade.
* Create an 'early_create' phase to call the create_ovs_tap()
function.
* Refactor the create_ovs_tap() function to accept an argument for
the network to use.
Change-Id: I0efe427a7023d0336f25856c362c655c138102df