Reduced too broad catch block

Author: trustin

src/main/java/org/jboss/netty/util/ThreadRenamingRunnable.java

@@ -63,7 +63,7 @@ public void run() {
         try {
             currentThread.setName(threadName);
             renamed = true;
-        } catch (Exception e) {
+        } catch (SecurityException e) {
             // Probably SecurityException.
         }