secchan: When we flush the flow table, add the in-band control rules back in.

secchan: When we flush the flow table, add the in-band control rules back in.

ofproto_flush_flows() deletes all the flows from the flow table, even the
ones added by in-band control.  If that happens we need to add them back
in.

This should be the only place that the in-band control rules can get
deleted, since their priorities are such that the controller cannot see
or modify them.