A random minute in the 21st hour UTC, daily, was chosen arbitrarily.
That it is run on a single arbitrary host from the set was done to
prevent unnecessary work being done until Bug #1424705 provides us with
a cleaner solution.
Adjusted to run once per day just to be sure that the operation doesn't
lock the table for a meaningful duration.
Making this configurable or tunable does not seem
to be necessary at this time.
Change-Id: I87164926a4d6a65d3c9f733d625a2d4af91c2597
Closes-Bug: #1466126
4ab9496724