From avagin@:
  And here is one more problem. the newroot directory is created for all
  controllers, but currently test cleans up it only for the zdtmtst
  controller. We need to find a way to clean up all other conntrollers.
   Tests are executed on a node, which is rebooted only for updating
  kernel, so if we will not clean up all other controllers, we can eat all
  memory.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Tested-by: Andrew Vagin <avagin@openvz.org>