Ramp up the delay on subsequent attempts. Fast builders have the same delay.

Not a perfect fix, but should make it better. And this easy.

Fixes #9903 maybe
Fixes #10680 maybe

Change-Id: I967380c2cb8196e6da9a71116961229d37b36335
Reviewed-on: https://go-review.googlesource.com/9795Reviewed-by: Matthew Dempsky <mdempsky@google.com>