Add test for dumping\restoring unnamed unix sockets.

* Added test for dumping\restoring of unnamed unix sockets.
  Also test added to test/Makefile. Use make run for launch.

* Cleanup env after call run.sh in test/libcriu.

Signed-off-by: Artem Kuzmitskiy <artem.kuzmitskiy@lge.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>