The nil FlowOp check in collectFlowOps was not addressed with the
introduction of DiscardingFlowOp. This meant that DiscardingFlowOps
produced in the router core would get handled by fastdp as if they were
foreign FlowOps, preventing flow creation and so leading to unwarranted
ODP misses.
To fix this, collectFlowOps cannot simply eliminate FlowOps for which
Discards() is true, because it's true for odpFlowKeyFlowOp. So the
Discards() case has to be handled in FastDatapath send().
David Wragg
27367ab292