The backoff function and parameters have been pulled up into an
interface `backoffStrategy`. The default parameters are now part of a
package variable `DefaultBackoffConfig`. The strategy is then plumbed
through `dialOptions`. As a result of this PR, the
maximum backoff delay can now be set using the `WithBackoffConfig` dial
option.
While the addition of strategy may seem premature, this allows one to
simply export `BackoffStrategy` and `WithBackoff` to allow arbirarily
configurable backoff strategies.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
Stephen J Day