Add a new config option to SLO, allow_async_delete, to allow operators
to opt-in to this new behavior. If their expirer queues get out of hand,
they can always turn it back off.
If the option is disabled, handle the delete inline; this matches the
behavior of old Swift.
Only allow an async delete if all segments are in the same container and
none are nested SLOs, that way we only have two auth checks to make.
Have s3api try to use this new mode if the data seems to have been
uploaded via S3 (since it should be safe to assume that the above
criteria are met).
Drive-by: Allow the expirer queue and swift-container-deleter to use
high-precision timestamps.
Change-Id: I0bbe1ccd06776ef3e23438b40d8fb9a7c2de8921
e78377624a