Fix recheckwatch sorting.

It was reversed.

And subject to a theroretical zero-div bug, but unlikely due to
timing.

Change-Id: I1e9653889033cc77075a4c806535a71e2ef456d6
Reviewed-on: https://review.openstack.org/19959
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins