rgw: gc remove tag issue
Currently a gc tag is removed once the first shadow object is removed. That is problematic since if there is a failure in removing the rest of the shadow objects, there's no record to do so.
Instead we should only remove the gc tag once all the shadow objects are successfully removed.
now gc add tag to remove queue just after first shadow io finish,
so if following shadows have any delete failure, there will be no chance to retry, since gc tag entry have been removed.