competing calls on the same object on versioned bucket
mutating calls on the same object may unexpected have
higher delays.
This can be reproduced with a replicated bucket
overwriting the same object writes, deletes repeatedly.
For longer locks like scanner keep the 1sec interval
* Fix cases where minimum timeout > default timeout.
* Add defensive code for too small/negative timeouts.
* Never set timeout below the maximum value of a request.
* Protect against (unlikely) int64 wraps.
* Decrease timeout slower.
* Don't re-lock before copying.
