iterate over retry_delays

[DrChainsaw]

Fixes #171

I have run some manual testing to add procs as well as testing with with a non-public package which depends on ClusterManagers.

@tanmaykm I'm not 100% I understood all aspects of the code so I'd be happy if you can take a look at this. I suppose there are alot of edge cases which might not be covered by my testing.

[tanmaykm]

Yes, using the iterator seems a lot better. Thanks!

[DrChainsaw]

Thanks!

I rewrote the logic so it tries to parse the host and port before going into the retry loop. Besides resolving the bytestr scope issue it should also do the expected thing if the user supplies an empty iterator for the retry_delays.

[DrChainsaw]

Bump.