drop toString in favour of constructing a "message" for the super class

By setting the message we get better error reporting in apps that call
getMessage() during error reporting rather than toString(). Clojure
appears to be an example of this.

And becasue the super class (RuntimeException) has a sensible
toString method that takes into account the class name and message we
do not our own toString method.

Author: Matthias Radestock

src/com/rabbitmq/client/ShutdownSignalException.java

@@ -66,6 +66,10 @@ public ShutdownSignalException(boolean hardError,
                                    boolean initiatedByApplication,
                                    Object reason, Object ref)
     {
+        super((initiatedByApplication
+               ? ("clean " + (hardError ? "connection" : "channel") + " shutdown")
+               : ((hardError ? "connection" : "channel") + " error"))
+              + "; reason: " + reason);
         this._hardError = hardError;
         this._initiatedByApplication = initiatedByApplication;
         this._reason = reason;
@@ -88,13 +92,6 @@ public ShutdownSignalException(boolean hardError,
     /** @return Reference to Connection or Channel object that fired the signal **/
     public Object getReference() { return _ref; }
 
-    public String toString() {
-        return super.toString() + " (" +
-            (_initiatedByApplication
-                    ? ("clean " + (_hardError ? "connection" : "channel") + " shutdown")
-             : ((_hardError ? "connection" : "channel") + " error"))
-            + "; reason: " + _reason + ")";
-    }
 }