Previously, requests involving DLOs would bypass versioned_writes:
* Any existing DLOs wouldn't get copied to the archive container during
overwrites (or deletes, with history-mode), so there would be no
evidence they had ever existed.
* Any new DLOs wouldn't copy overwritten objects to the archive
container, potentially leading to data loss.
Now, DLOs will behave like every other type of object under
versioned_writes.
Change-Id: I488e13eead2f33dd272d03f6f898adc52fc7fdad
Related-Change: Ie899290b3312e201979eafefb253d1a60b65b837
Related-Change: Ib5b29a19e1d577026deb50fc9d26064a8da81cd7
Closes-Bug: #1626989