1. d4n/directory: Update logging
2. d4n/filter: Update `set_head_obj_dir_entry` to handle null versioning and update `prevVersion` for versioned head objects
3. rgw/d4n: Simplify code to only support unversioned bucket deletes
+ if (!this->get_bucket()->versioning_enabled() && block.version == "null") { // null delete markers get overwritten but only if versioning is suspended
+ ldpp_dout(dpp, 10) << "D4NFilterObject::" << __func__ << "(): BlockDirectory set method failed for versioned head object with ret: " << ret << dendl;