inet: dump actual states of tcp sockets

We get sockets from task_diag, then we block network and dump sockets.

A socket state can be changed between first two steps, so lets get
a socket state on the third step and dump it.

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>