S3: prevent deleting buckets with object locking (#7434)

* prevent deleting buckets with object locking

* addressing comments

* Update s3api_bucket_handlers.go

* address comments

* early return

* refactor

* simplify

* constant

* go fmt

weed/command/download.go

@@ -23,9 +23,9 @@ var (
 )
 
 type DownloadOptions struct {
-	master       *string
-	server       *string // deprecated, for backward compatibility
-	dir          *string
+	master *string
+	server *string // deprecated, for backward compatibility
+	dir    *string
 }
 
 func init() {