We are using tar for resting tmpfs. Currently we execute tar from a
restored root, but nobody guarantees that it is there and that it's
really tar.

We don't have reason to change root too early. Lets live in a source
root as long as we can, because we can be sure that it's consistent.

https://bugzilla.openvz.org/show_bug.cgi?id=2870

v2: remove redundant chdir()
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>