Add support for connecting to sentinel servers
All of the gitlab services in the chart have upstream support for using redis sentinel services, but our chart does not expose these options.
We should add sentinel configuration support to the chart. You should be able to provide the chart with your list of sentinel hosts and ports, and your masterSet and masterPort, and masterPassword, and be able to use sentinel.
This feature is blocking our ability to ship a redis with full sentinel support enabled out of the box. See: https://gitlab.com/charts/gitlab/issues/1221