vzctl: don't need to umount each mount points for cleaning up mntns (v2)

pivot_root moves the root file system of the current process to the
directory put_old and makes new_root the new root file system.

So put_old can be detached and all other mount points will be unvisible
from this mntns, because nobody holds them.

v2: delete more lines of code

[kir@openvz.org: now this looks exactly like my initial version :)]

Signed-off-by: Andrey Vagin <avagin@openvz.org>
1 file changed