object: set default zone/zonegroup/realm values for external rgw
object: set default zone/zonegroup/realm values for external rgw

currently if multisite is not configured Rook sets values for
zone/zonegroup/realm as object store name which is only valid for
internal ceph object store. This may not exists for rgw running in
external cluster.

Signed-off-by: Jiffin Tony Thottan <ac134a614b50f2e879db85acb9f4b45b24a210dc@gmail.com>

rook/rook,rook/rook,rook/rook,rook/rook,rook/rook