Revert "Changed from topidId --> _id to use the db field that hase index by default on the opinion model" because _id needs to be uniqe, this was an oversigth on my part. The topicId is almost never uniqe.

This reverts commit 1f031b4ed74546c42e5793876ddc00ed6df448e7.
Added cooldown period for the emitUpdateCurrentVoterCount