private void closeCache() {
		PathChildrenCache cache = cacheRef.get();
		if (cache != null) {
			try {
				cache.close();
			}
			catch (Exception e) {
				// ignore exception on close
			}
			finally {
				cacheRef.compareAndSet(cache, null);
			}
		}
	}
Close the {@link PathChildrenCache container cache} and null out
the {@link #cacheRef atmoic reference}.
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/container/store/ZooKeeperContainerRepository.java