criu: unset loginuid value before creating userns
criu: unset loginuid value before creating userns

The value of loginuid cannot be changed inside container, with the
exception if it was not set yet. This value is inherited on fork() from
parent.

So, to restore original loginuid values for all tasks:
  - unset the container parent loginuid
  - all children will have this value unsetted
  - on child restore set value from dump

See http://lxr.free-electrons.com/source/kernel/audit.c#L635
https://jira.sw.ru/browse/PSBM-41993

Signed-off-by: Dmitry Safonov <5aea3f9692c8a01793193334616ae8fad2bc748a@odin.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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