datapath-windows: Enable extension after rrestart

datapath-windows: Enable extension after rrestart

The extension failed to be activated during booting due to the
failure to initialize tunnel filter. This happened because the Base
Filtering Engine (BFE) is not started and no session to the engine
could be acquired.

The solution for this was to registered a BFE notification callback
that is called whenever the BFE's state changes. Only if the BFE's
state is running the tunnel filter is initialized.

Signed-off-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Reported-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Reported-at: https://github.com/openvswitch/ovs-issues/issues/77
Acked-by: Eitan Eliahu <eliahue@vmware.com>
Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>