pstree: Allow to dump and restore session non-leaders if --shell-job passed
pstree: Allow to dump and restore session non-leaders if --shell-job passed

If --shell-job passed we allow to dump and restpre session non-leaders.

Note that in sake of tty restore (which will be addressed in
further patches) we do inherit process group for root task.

Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@openvz.org>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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