CLC-3190: LiveUpdates: UpNext merged feed cache should expire at midnight every night

https://jira.media.berkeley.edu/jira/browse/CLC-3190

The UpNext merged feed now expires at midnight every night
instead of never expiring. Now, it will be fresh every day,
and should no longer show old data for first-time-in-the-morning logins.
Merge pull request #2065 from chikoon/CLC-3190-expire-upnext-at-midnight

CLC-3190: LiveUpdates: UpNext merged feed cache should expire at midnight every night