Fixed a stack overflow exception if one println()'ed

a service... since most service managers print their
services in their own toString().

jme3-networking/src/main/java/com/jme3/network/service/AbstractService.java

@@ -106,6 +106,6 @@ public abstract class AbstractService<S extends ServiceManager> implements Servi
     
     @Override
     public String toString() {
-        return getClass().getName() + "[serviceManager=" + serviceManager + "]";
+        return getClass().getName() + "[serviceManager.class=" + serviceManager.getClass() + "]";
     }
 }