I changed this in https://github.com/hashicorp/consul/pull/8802#pullrequestreview-500779357 because
exceeding the MaxWait seemed wrong, but as other have pointed out, that behaviour is probably correct.
When multiple waiters hit the max value, we don't want them to converge, so restore the behaviour of
allowing jitter to exceed max, and document it.
Reduce Jitter to one function
Rename NewRetryWaiter
Fix a bug in calculateWait where maxWait was applied before jitter, which would make it
possible to wait longer than maxWait.
The fields are only ever read by Waiter, and
setting the fields makes the calling code read much better without
having to create a bunch of constants that only ever get used once.
