* Create helpers for processes which have been reparented to init.
* Insert helpers in a process tree.
* Helpers will exit after constructing a process tree.

v2: fix variables names and check errors
v3: add comments in code
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>