[IO/Config] Retry up to 3 times on init.

- tries to fetch config up to 3 times with linear delay.
- tries to create connection/channel up to 3 times with linear delay.
[Config] Don't sleep on last try as it just wastes time.
Merge pull request #11 from soomo/safer-init

[IO/Config] Retry up to 3 times on init.