datapath-windows: Solved BSOD when adding OVS ports

datapath-windows: Solved BSOD when adding OVS ports

This BSOD occurred in the context of a packet (NBL) with multiple
NET_BUFFER(s) (NBs). The reason for the BSOD is due to the marking
of NBLs created by OVS as being external and wrongly completing them.

Signed-off-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Reported-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Reported-at: https://github.com/openvswitch/ovs-issues/issues/82
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>