Add options to support multiple redis instances behind the same hostname

[msoedov]

Hi,

We have a use case when we running N ( where N could be 10, 20 ....) redis servers with dynamic ip addresses and dns based service discovery. So we have a hostname like redis-privatenet.com which resolves to N servers.

My proposal is the following:

1. Resolve hostname to list of ip addresses initially
2. Re -resolve that hostname on connection failure to one of the nodes
3. Re -resolve the hostname periodically (with ~30 sec inteterval) to discover recently joined redis nodes.

I am ready to make a patch just wanted to discuss the approach here first.

Any thoughts?