Use github.com/cenkalti/backoff for retries

[rjoleary]

Use github.com/cenkalti/backoff to replace the backoff algorithm in #296.

The backoff package is well tested and gives the user more control over which backoff method and parameters to use.

[rjoleary]

I can work on this.

[insomniacslk]

Thanks for working on this! On a phone now and can't remember what was wrong with the current retry system, are you addressing a particular problem that hit you?

[rjoleary]

There'd be two main benefits for using this library. First, it would give more control/options over how the backoff is performed (especially with the BackOff interface). Secondly, this backoff library is well tested.

[rjoleary]

It doesn't look like this repository has a vendor directory. How would you want to make the dependency on github.com/cenkalti/backoff ?

[hugelgupf]

I'd just make it without managing it, same as with u-root so far.

When u-root is ready we should go to modules?

[pmazzini]

I can work on this.

@rjoleary Are you looking at this?

[heinz-boehmer]

I'll take over this.