Any step can set the number of times it should be attempted by attaching an
attempts parameter with the number of times it should be tried.
Attempts will retry on a Concourse error as well as build failure.
The total number of times a step should be tried should it fail, e.g.
5 will try the step up to 5 times before giving up.
When the number of attempts is reached and the step has still not succeeded then the step will fail.