add 502 status code to DefaultRetryStrategy

Author: liyanzhang505

src/main/java/com/aliyun/oss/common/comm/DefaultServiceClient.java

@@ -214,8 +214,8 @@ public boolean shouldRetry(Exception ex, RequestMessage request, ResponseMessage
 
             if (response != null) {
                 int statusCode = response.getStatusCode();
-                if (statusCode == HttpStatus.SC_INTERNAL_SERVER_ERROR
-                        || statusCode == HttpStatus.SC_SERVICE_UNAVAILABLE) {
+                if (statusCode == HttpStatus.SC_INTERNAL_SERVER_ERROR || statusCode == HttpStatus.SC_BAD_GATEWAY ||
+                        statusCode == HttpStatus.SC_SERVICE_UNAVAILABLE) {
                     return true;
                 }
             }