The correct total retry time should be:
  c + c * b^1 + (...) + c*b^(k - 1)

But the previous implementation was:
  c + c * b^0 + c * b^1 + (...) + c*b^(k - 1)

where:

  * c: constant factor, @retry_wait
  * b: base factor, @retry_exponential_backoff_base
  * k: number of retry times, @max_retry_times

Although the first retry interval is already added at constructor of
ExponentialBackoffRetry, same value is added again unexpectedly on the
first calc_interval call (as `c * b^0`).

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

The previous implementation detects @max_retry_times + 1 as limit,
but the limit should be @max_retry_times.

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

RetryStatement behavior is complicated, so scenario tests may be useful.

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Add 2 states to control timeout.

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Signed-off-by: Takuro Ashie <ashie@clear-code.com>