ofproto-dpif: Make OFPP_TABLE always resubmit to table 0.

ofproto-dpif: Make OFPP_TABLE always resubmit to table 0.

Commit 299016266ed1 (New action NXAST_RESUBMIT_TABLE.) changed OFPP_TABLE
from resubmitting to table 0 to resubmitting to the current table.  This
wasn't mentioned in the change log and I believe it was a typo.  This
commit changes the behavior back.

This isn't a very serious bug because OpenFlow 1.0 says that OFPP_TABLE is
supposed to be used only in packet-out messages, in which case the current
table is 0 anyhow.

OpenFlow 1.3 is explicit:

    The action list of an OFPT_PACKET_OUT message can also specify the
    OFPP_TABLE reserved port as an output action to process the packet
    through the existing flow entries, starting at the first flow table.

Reported-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Ben Pfaff <blp@nicira.com>