rgw: add force option to `radosgw-admin object rm ...`

rgw: add force option to `radosgw-admin object rm ...`

The `radosgw-admin object rm ...` sub-command will give up if it
determines that there's an issue with the head object. This can make
it difficult for an admin to clean up a bucket index when there's a
damaged or missing head object.

When the user adds the "--yes-i-really-mean-it" command-line option,
it enables the "force mode". The bucket index entry(ies) will be
removed. If the object being removed is the current version in a
versioned bucket, the appropriate changes to the OLH will take place.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>