Expire the CURRENT_RELEASES cache every day
We cache it so we're not constantly re-discovering this every
time a test completes (that seems a little excessive), but
caching it *forever* is wrong too, as every few months we
either branch or cut a release. Currently I have to remember to
restart fedmsg-hub when this happens, or else nightlies keeps
showing the table for the release that was cut, or *doesn't*
add a table for the new Branched release.
This way, I don't have to remember that, within a day or so of
the branch happening or a release happening, nightlies will
refresh and clean up the data automatically.
Signed-off-by: Adam Williamson <awilliam@redhat.com>