DefaultCacheManager should stop components after start failure

Currently it is impossible to release all the resources allocated during startup if the DefaultCacheManager instance was created with start=true. The user has to do something like this:

DefaultCacheManager manager = new DefaultCacheManager(..., false);
try {
   manager.start();
} catch (Throwable t) {
   manager.stop();
   throw t;
}

Both the constructor and the public start() method should clean up the started components after a startup failure, so that the user doesn't have to call stop() explicitly.

Our tests do not currently call stop() explicitly, so they leak threads and sockets when a manager fails to start (e.g. because something went wrong with the CONFIG cache).