CURATOR-33 recursive TreeCache recipe

In such a case, it won't actually initialize the entire tree twice, only the root node itself.  That's what I was trying to get at in my earlier comment: "if two threads are trying to concurrently add a new node "/test/foo" to an existing node "/test", only one thread can win; so duplicate events inherently don't propagate down the tree".  In other words, only one thread will actually do the recursive fetch on '/test/foo' and continue exploring that subtree.