365731510976 (bug 1380391) added index routes for decision tasks by
pushlog id. This is a good idea. The pushlog id is guaranteed to always
be incrementing (except for repos that are periodically reset, which
we don't care about). It is useful to provide strict ordering for
pushes and is simpler for machines to consume and sort than dates.
So let's index all tasks by pushlog id.
MozReview-Commit-ID: BPqx4ARza1c
--HG--
extra : rebase_source : e952c636e5fcd2a0ddb5e14a0faaccb3761298bf