Allow DIH to report its state to ZooKeeper

I thought it may be good to be able for DIH to be fully controllable by Solr in SolrCloud. So when once instance fails another could be automatically started and so on. This issue is the first small step there - it makes SolrCloud report DIH state to ZooKeeper once it is started and remove its state once it is stopped or indexing job failed. In non-cloud mode that functionality is not used.