LPS-48408 As a system administrator I'd like to be able to take cluster wide thread dumps to help support diagnose my problem

Hi Tina,

I took LuceneHelperImpl.LoadIndexClusterResponseCallback as an example for implementing the callback. The last commit is a new idea which will help us and customers to see where thread dumps stemmed from.

Please let me know if you have any further suggestions. 

Thanks,
László

/CC: @mhan810