Fix config length limitation. (#623)

Author: weixiang1862

CHANGES.md

@@ -14,6 +14,7 @@ Release Notes.
 * Optimize spring-cloud-gateway 2.1.x, 3.x witness class.
 * Support report MongoDB instance info in Mongodb 4.x plugin.
 * To compatible upper and lower case Oracle TNS url parse.
+* Fix config length limitation.
 
 #### Documentation
 

apm-commons/apm-util/src/main/java/org/apache/skywalking/apm/util/ConfigInitializer.java

@@ -96,7 +96,7 @@ private static void initNextLevel(Properties properties, Class<?> recentConfigTy
                                 }
                             }
                             if (propertyValue.length() > lengthLimited) {
-                                StringUtil.cut(propertyValue, lengthLimited);
+                                propertyValue = StringUtil.cut(propertyValue, lengthLimited);
                                 System.err.printf("The config value will be truncated , because the length max than %d : %s -> %s%n", lengthDefine.value(), configKey, propertyValue);
                             }
                         }