ofproto-dpif: Update bundle when OFPPC_NO_FLOOD changed.

When the OFPPC_NO_FLOOD flag is toggled on the port, the "floodable"
member of the bundle was not updated.  This would cause OFPP_NORMAL to
not include the proper ports when flooding.  With this commit,
OFPPC_NO_FLOOD changes will cause the floodable members to be
recalculated.

Found by inspection.