api: No need to set x-amz-bucket-region if region is empty. (#4586)

cmd/api-headers.go

@@ -36,7 +36,11 @@ func setCommonHeaders(w http.ResponseWriter) {
 	// Set unique request ID for each reply.
 	w.Header().Set(responseRequestIDKey, mustGetRequestID(UTCNow()))
 	w.Header().Set("Server", globalServerUserAgent)
-	w.Header().Set("X-Amz-Bucket-Region", serverConfig.GetRegion())
+	// Set `x-amz-bucket-region` only if region is set on the server
+	// by default minio uses an empty region.
+	if region := serverConfig.GetRegion(); region != "" {
+		w.Header().Set("X-Amz-Bucket-Region", region)
+	}
 	w.Header().Set("Accept-Ranges", "bytes")
 }