After the introduction of the CloseableExecutorService (see
CURATOR-17) the PathChildrenCache may create Executor services that it doesn't close.
Ideally, the CloseableExecutorService should accept a parameter that specifies if the executor needs to be shutdown on close. Recipes that create their own ExecutorService should set this parameter to true. When an executor not directly managed by the recipe is used, the flag should be just false, so that the the executor doesn't always close (satisfy