bugfix: the thread-level classloader in ConfigManager is switched to …

…the instance-level classloader (#69)

trpc-core/src/main/java/com/tencent/trpc/core/common/ConfigManager.java

@@ -281,7 +281,7 @@ protected void startInternal() throws Exception {
             // 7) register service
             serverConfig.register();
             // 8) cache startup class loader
-            cachedClassLoader = Thread.currentThread().getContextClassLoader();
+            cachedClassLoader = ConfigManager.getInstance().getClass().getClassLoader();
         }
 
         private void warmupCodec() {