Update from 2.6.10 to 2.6.11.
UPGRADE URGENCY: LOW, however updating is encouraged if you have many instances
per server and you want to lower the CPU / energy usage.
* [BUGFIX] Replication: more strict error checking for master PING reply.
* [BUGFIX] redis-cli: use keepalive socket option for improved reliability.
* [BUGFIX] Allow AUTH while loading the DB in memory.
* [BUGFIX] Don't segfault on unbalanced quotes while parsing config file.
* [IMPROVED] serverCron() frequency is now a runtime parameter (was REDIS_HZ).
* [IMPROVED] Use a lot less CPU when idle, even with many configured DBs.