Race condition on ArtifactoryConfigLoader.load

https://github.com/apache/storm/blob/master/storm-server/src/main/java/org/apache/storm/scheduler/resource/ResourceAwareScheduler.java#L100-L102

config() is called in multiple threads. But ArtifactoryConfigLoader.load is not thread-safe. For example, https://github.com/apache/storm/blob/master/storm-server/src/main/java/org/apache/storm/scheduler/utils/ArtifactoryConfigLoader.java#L181-L187

JSONObject returnValue;
        try {
            returnValue = (JSONObject) jsonParser.parse(metadataStr);
        } catch (ParseException e) {
            LOG.error("Could not parse JSON string {}", metadataStr, e);
            return null;
        }

Multiple threads use the same jsonParser and since JsonParser is not thread-safe, the return value will be corrupted.

I propose to create a separate thread to load scheduler configs periodically. This also makes the config loading logic cleaner.