node: Make OVS switches reconnect quickly

Ordinarily, OVS switches back off when they can't reach their controllers.
Under the type of scenarios where Mininet is used, I think this is
probably just inconvenient.  This patch set controllers to attempt to
reconnect every second.
Merge pull request #150 from MurphyMc/ovs_fast_reconnect

node: Make OVS switches reconnect quickly