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.
most register waits could use a very short (a few usecs) timeout.  i'll see if it's reasonable to add it as an optional argument without adding too much weight to the function.
I don't think we could reasonably skip some of these specific waits, (specially at the receive part), releasing a descriptor before it's appropriate might make a packet fall anywhere in RAM.