returns the root device node. Now its actually possible to
traverse the device node tree without a node to start with.
* Fixed execution order problem in dm_get_next_child_node(). The
supplied node was put first (which could cause its immediate
deletion), but was still accessed thereafter.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@16268 a95241bf-73f2-0310-859d-f6bbb57e9c96