Update from 2.8.0-rc2 to 2.8.0-rc3.
Disable debug flags.
# UPGRADE URGENCY: HIGH
* [FIX] Improved expired keys collection algorithm. Even under heavy load keys
to be expired can't accumulate because of lack of CPU time.
* [FIX] Replication speed regression fixed (issue #1238).
* [FIX] Fixed an hard to trigger PSYNC bug.
* [FIX] Fixed Issue #1240, ZUNIONSTORE could lead to wrong result.
* [NEW] Add per-db average TTL information in INFO output.
* [NEW] redis-benchmark improvements.
* [NEW] dict.c API wrong usage detection.