#6336 causes overlord console page loading to be extreme slow

As discussed in [#6336 (comment)](https://github.com/apache/incubator-druid/pull/6336#issuecomment-446211138), I think we should revert #6336 first and find a better way to complete #6336. How do you think @FaxianZhao @jihoonson.

Start by reading PR #6336 and the linked issue comment to understand the change associated with the regression. Reproduce the slow Overlord console page loading, then determine whether reverting #6336 resolves it and document a better replacement approach.

Written by the indexing model from the issue text.