zdtm: Add sock_peercred test

Check that SO_PEERCRED socket options restored correctly.
Now it's not supported, thus test is marked as "noauto".

(It seems support of this feature will require "ghost tasks",
when we introduce them).

travis-ci: success for zdtm: Add sock_peercred test
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>