Uri.toUrl should reset underlying StringBuilder, close AsyncHttpClient#800

Author: Stephane Landelle

api/src/main/java/org/asynchttpclient/uri/Uri.java

@@ -105,8 +105,8 @@ public String toUrl() {
                 sb.append(path);
             if (query != null)
                 sb.append('?').append(query);
-
             url = sb.toString();
+            sb.setLength(0);
         }
         return url;
     }