rgw: fix 'bucket rm --bypass-gc' for copied objects

rgw: fix 'bucket rm --bypass-gc' for copied objects

the `--bypass-gc` argument to `radosgw-admin bucket rm` causes us to
call `RadosBucket::remove_bypass_gc()`, which loops over the tail
objects and removes each with `RGWRados::delete_raw_obj_aio()`

however, this was removing the objects with `cls_rgw_remove_obj()`,
which is for head objects, not tails. tail objects must be removed with
`cls_refcount_put()`, which preserves them until the last copy is
removed

rename `delete_raw_obj_aio()` to `delete_tail_obj_aio()` to clarify its
purpose

Fixes: https://tracker.ceph.com/issues/73348
Signed-off-by: Casey Bodley <cbodley@redhat.com>