fs: Handle no buckets (#12531)
fs: Handle no buckets (#12531)

Since total are sent after each bucket, deleting all would 
not make usage go to zero.
balamurugana/minio,NitishT/minio,donatello/minio,balamurugana/minio,donatello/minio,minio/minio,krisis/minio,NitishT/minio,krisis/minio,minio/minio,NitishT/minio,vadmeste/minio,vadmeste/minio,NitishT/minio