Updated comments in wait.go
Updated comments in wait.go

The comments on the fields of Backoff did not match the behavior of
the Step() method.

The comment on the Step method did not make it clear whether the
returned amount of time to sleep is based on the original or the
revised duration.

The comments on the ExponentialBackoff function did not exactly and
clearly correspond to the actual behavior.

Kubernetes-commit: 529a168be99435bd6cd2351d4f3ce349e1628772

kubernetes/apimachinery