Do not use InstallState in PluginManager when loading detached plugins

core/src/main/java/hudson/PluginManager.java

@@ -679,9 +679,8 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
      * </ul>
      */
     protected void loadDetachedPlugins() {
-        InstallState installState = Jenkins.getActiveInstance().getInstallState();
-        if (InstallState.UPGRADE.equals(installState)) {
-            VersionNumber lastExecVersion = new VersionNumber(InstallUtil.getLastExecVersion());
+        VersionNumber lastExecVersion = new VersionNumber(InstallUtil.getLastExecVersion());
+        if (lastExecVersion.isNewerThan(InstallUtil.NEW_INSTALL_VERSION) && lastExecVersion.isOlderThan(Jenkins.getVersion())) {
 
             LOGGER.log(INFO, "Upgrading Jenkins. The last running version was {0}. This Jenkins is version {1}.",
                     new Object[] {lastExecVersion, Jenkins.VERSION});

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

@@ -70,7 +70,7 @@ public class InstallUtil {
     private static final Logger LOGGER = Logger.getLogger(InstallUtil.class.getName());
 
     // tests need this to be 1.0
-    private static final VersionNumber NEW_INSTALL_VERSION = new VersionNumber("1.0");
+    public static final VersionNumber NEW_INSTALL_VERSION = new VersionNumber("1.0");
     private static final VersionNumber FORCE_NEW_INSTALL_VERSION = new VersionNumber("0.0");
 
     /**