ofproto-dpif: Make OFPP_TABLE send packet-in on miss.

ofproto-dpif: Make OFPP_TABLE send packet-in on miss.

The OpenFlow specification for OFPP_TABLE implies that a miss
should generate a packet-in, but Open vSwitch has never done
that.  This corrects the behavior.

This also prepares for the goto-table instruction, which will
need to generate a table-miss in some circumstances.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
[blp@nicira.com rebased and updated commit message]
Signed-off-by: Ben Pfaff <blp@nicira.com>