Logging enhancements, avoid stacktrace in WARN level.

joram/joram/mom/core/src/main/java/org/objectweb/joram/mom/proxies/tcp/TcpProxyService.java

 /*
  * JORAM: Java(TM) Open Reliable Asynchronous Messaging
- * Copyright (C) 2001 - 2019 ScalAgent Distributed Technologies
+ * Copyright (C) 2001 - 2020 ScalAgent Distributed Technologies
  * Copyright (C) 1996 - 2000 Dyade
  *
  * This library is free software; you can redistribute it and/or
@@ -154,8 +154,12 @@ public class TcpProxyService implements TcpProxyServiceMBean {
   	    serverSocket = new ServerSocket(port, backlog, InetAddress.getByName(address));
   	  }
     } catch (Exception exc) {
+  	  if (logger.isLoggable(BasicLevel.DEBUG))
       logger.log(BasicLevel.ERROR,
                  "TcpProxyService.createServerSocket(" + port + ',' + backlog + ',' + address + ')', exc);
+  	  else
+  	    logger.log(BasicLevel.ERROR,
+  	               "TcpProxyService.createServerSocket(" + port + ',' + backlog + ',' + address + "): " + exc.getMessage());
       throw exc;
     }