Use class name convention for file names

core/src/main/java/jenkins/install/InstallUtil.java

@@ -187,11 +187,11 @@ public class InstallUtil {
     }
 
     static File getLastExecVersionFile() {
-        return new File(Jenkins.getInstance().getRootDir(), "last_run_version");
+        return new File(Jenkins.getInstance().getRootDir(), "jenkins.install.InstallUtil.lastExecVersion");
     }
 
     static File getInstallingPluginsFile() {
-        return new File(Jenkins.getInstance().getRootDir(), "setup_wizard_installing_plugins");
+        return new File(Jenkins.getInstance().getRootDir(), "jenkins.install.InstallUtil.installingPlugins");
     }
 
     private static String getCurrentExecVersion() {

core/src/main/java/jenkins/install/UpgradeWizard.java

@@ -47,7 +47,7 @@ public class UpgradeWizard extends PageDecorator {
      * This file records the vesrion number that the installation has upgraded to.
      */
     /*package*/ File getStateFile() {
-        return new File(Jenkins.getInstance().getRootDir(),"last_upgrade_version");
+        return new File(Jenkins.getInstance().getRootDir(),"jenkins.install.UpgradeWizard.state");
     }
 
     public UpgradeWizard() throws IOException {