Bugs 913039 and 999066 - The return of the elasticsearch cleanup cron

@peterbe @phrawzty @lonnen the first commit is the same that was merged into master recently. I fixed what I believe caused the problem in the second commit. 

Basically: there were leftover indices, and they would cause problems the next week when unit tests would try to create an aliases with last week's index name. I have verified that no index is left in my local ES after running the entire test suite. We will be sure the problem is gone the week after we merge this. :)