@Override
    public void register(SingletonWorker singleton, Duration timeout) {
        try {
            await(singletons.register(singleton.id(), singleton), timeout, "registering " + singleton);
        }
        catch (RuntimeException e) {
            try {
                unregister(singleton, timeout);
            }
            catch (Exception f) {
                e.addSuppressed(f);
            }
            throw e;
        }
    }
Implementation of {@link VespaCurator} which delegates to a {@link Curator}.
This prefixes all paths with {@code "/user"}, to ensure separation with system ZK usage.

@author jonmv
zkfacade/src/main/java/com/yahoo/vespa/curator/CuratorWrapper.java