datapath-windows/Flow.c: FLOW_SET command handler.

datapath-windows/Flow.c: FLOW_SET command handler.

Registered FLOW_SET command handler. The same command
handler as FLOW_ADD is good enough to handle FLOW_SET
case as well.

Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Eitan Eliahu <eliahue@vmware.com>
Acked-by: Nithin Raju <nithin@vmware.com>
Acked-by: Samuel Ghinet <sghinet@cloudbasesolutions.com>
Tested-by: Ankur Sharma <ankursharma@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>