TCP_CLOSE_WAIT remote side has shutdown and is waiting for
               us to finish writing our data and to shutdown
               (we have to close() to move on to LAST_ACK)

TCP_LAST_ACK   out side has shutdown after remote has
               shutdown.  There may still be data in our
               buffer that we have to finish sending

travis-ci: success for series starting with [01/21] build: install libnet-dev
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>