looks a bit ugly but was the cleanest solution i could come up with. the rationale is:

i can add a node, add some children to it, move the children elsewhere and then remove the parent node again, and only at the end of all that flush. this might be some import workflow or whatever. in jsop the cost of this additional step should be ok. otherwise it would become a LOT more complex inside the ObjectManager if we would want to exactly calculate the minimal changeset to get from the storage state to the local node state of the tree.