precondition check was being honored before, validating
if anonymous access is allowed on the metadata of an
object, leading to metadata disclosure of the following
headers.
```
Last-Modified
Etag
x-amz-version-id
Expires:
Cache-Control:
```
although the information presented is minimal in nature,
and of opaque nature. It still simply discloses that an
object by a specific name exists or not without even having
enough permissions.
NOTE: This feature is not retro-active; it will not cater to previous transactions
on existing setups.
To enable this feature, please set ` _MINIO_DRIVE_QUORUM=on` environment
variable as part of systemd service or k8s configmap.
Once this has been enabled, you need to also set `list_quorum`.
```
~ mc admin config set alias/ api list_quorum=auto`
```
A new debugging tool is available to check for any missing counters.
