redis: updated to 6.0.7

Redis 6.0.7

Upgrade urgency MODERATE: several bugs with moderate impact are fixed,
Specifically the first two listed below which cause protocol errors for clients.

Bug fixes:

* CONFIG SET could hung the client when arrives during RDB/ROF loading (When
  processed after another command that was also rejected with -LOADING error)
* LPOS command when RANK is greater than matches responded wiht broken protocol
  (negative multi-bulk count)
* UNLINK / Lazyfree for stream type key would have never do async freeing
* PERSIST should invalidate WATCH (Like EXPIRE does)
* EXEC with only read commands could have be rejected when OOM
* TLS: relax verification on CONFIG SET (Don't error if some configs are set
  and tls isn't enabled)
* TLS: support cluster/replication without tls-port
* Systemd startup after network is online
* Redis-benchmark improvements
* Various small bug fixes

New features:

* Add oom-score-adj configuration option to control Linux OOM killer
* Show IO threads statistics and status in INFO output
* Add optional tls verification mode (see tls-auth-clients)

Module API:

* Add RedisModule_HoldString
* Add loaded keyspace event
* Fix RedisModuleEvent_LoadingProgress
* Fix RedisModuleEvent_MasterLinkChange hook missing on successful psync
* Fix missing RM_CLIENTINFO_FLAG_SSL
* Refactor redismodule.h for use with -fno-common / extern

(adam)