For that we need to save per-namespace mappings of user and group IDs.

And all id-s for tasks and files are saved from the target user
namespace.

v2: move code into collect_namespaces()
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>