zdtm: check restore of TCP connections (v2)

The test creates two processes.
A first process creates a tcp server, a second one connects to it.
The first process is dumped and restored.
Then the test checks that the TCP connection is alive.

v2: fix compilation :)

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>