@Override
    public Optional<Meta> write(Path path, byte[] data, int expectedVersion) {
        try {
            return Optional.of(new Meta(curator.set(userRoot.append(path), data, expectedVersion).getVersion()));
        }
        catch (RuntimeException e) {
            if (e.getCause() instanceof BadVersionException) return Optional.empty();
            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