redis2_sentinel and redis3_sentinel stores only passed Username/Password
into redis.FailoverOptions, which authenticates against the Redis
master/replica servers. When Sentinel itself requires auth (requirepass
set in sentinel.conf), go-redis had no credentials to send to it,
causing a NOAUTH error before ever reaching the master.
Add sentinel_username/sentinel_password config options that map to
go-redis's SentinelUsername/SentinelPassword fields, distinct from the
existing master auth credentials.
TJDawson10andGitHub
b50116ccae