Early we moved prepare_shared() to a root task,
because several preparation actions should be executed
in a target namespace set (e.g.: ghost files).

TCP sockets are a subset of init sockets,
they should be unlocked before resume. It's convient to do
from crtools.
An image can't be read more than one time, because we want to
send it via network.

For this two reasons prepare_shared is spitted in two parts,
one for crtools and one for a root task.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>