Keep nfv

I added both `:close()` and `:reconfig()` methods to Intel10g (had to fix a little on app.lua for the second one).

The `:close()` is still missing deallocations, but the `:reconfig()` works on the "diff_vlans => same_vlan" test.
The `reenable` parameter never seems to be used. Is it needed? (a bit funny for a function called `disable_receive` to enable. Maybe better to have a separate `reset_receive` function for that if needed?)