Added redis replication attributes

This will add a master_ip and master_port option which can be used to enable redis replication for a HA solution

@marin can you have a look?

mentioned in issue gitlab-com/operations#5 (closed)

Status changed to closed

We don't need this to setup replication, use the redis commands instead.

@jnijhof Out of curiosity, what are the redis commands?

@marin instead of defining slave settings in config and restarting redis you can simply add/remove replication by:

/opt/gitlab/embedded/bin/redis-cli slaveof <master ip> 6379

And you can use the following command to convert a replication instance to master by:

/opt/gitlab/embedded/bin/redis-cli slaveof no one

@jnijhof great, thanks!

cc @dblessing

We need to document this. As I understand, a user will have to promote the slave manually? Also, we need to note that if you run reconfigure it will overwrite the configuration and make it a slave again, right?