samza-autoscaling YarnUtils json deserialisation fails with list values

Current:

The getRunningAppId method in org.apache.samza.autoscaling.utils.YarnUtil attempts to deserialise the json from this endpoint /ws/v1/cluster/apps on the resource manager into the following shape: <Map<String, Map<String, List<Map<String, String>>>>>

The problem is that when there is a running job there is a property called resourceRequests which has a json array as a value. Therefore Jackson throws an exception when it tries to deserialise a json array into a string.

Proposed:

Deserialise the json into the following structure: <Map<String, Map<String, List<Map<String, Object>>>>>. The only property being queried for is the `state` so I think this is appropiate.

I have written the first test for this module. Very open to feedback and improvements.