secchan: Retain original input port for NXAST_RESUBMIT action.

secchan: Retain original input port for NXAST_RESUBMIT action.

The NXAST_RESUBMIT action causes a secondary lookup in the flow table with
a different input port value.  However, we want to retain the original
input port for processing the result of that secondary lookup.  Otherwise,
output to OFPP_IN_PORT will send the packet to the wrong port, and output
to the input port without specifying OFPP_IN_PORT will be mistakenly
allowed.