[JENKINS-72799] Apply SlaveComputer.decorate also to openLogFile (#9009)

Author: jglick

core/src/main/java/hudson/slaves/SlaveComputer.java

@@ -386,7 +386,7 @@ public boolean isConnecting() {
     public OutputStream openLogFile() {
         try {
             log.rewind();
-            return log;
+            return decorate(log);
         } catch (IOException e) {
             logger.log(Level.SEVERE, "Failed to create log file " + getLogFile(), e);
             return OutputStream.nullOutputStream();