fix: the jenkins shutdown banner now renders correctly on all 4 pages

Author: ayush00git

core/src/main/resources/hudson/PluginManager/available.jelly

@@ -32,7 +32,7 @@ THE SOFTWARE.
     <!-- no need for additional breadcrumb here as the side panel offers enough functionality to browse between different pages -->
 
     <l:main-panel>
-      <div class="jenkins-app-bar jenkins-app-bar--sticky">
+      <div class="jenkins-app-bar ${app.isQuietingDown() ? '' : 'jenkins-app-bar--sticky'}">
         <div class="jenkins-app-bar__content">
           <l:search-bar clazz="jenkins-search--app-bar"
                         placeholder="${%Search available plugins}"

core/src/main/resources/hudson/PluginManager/installed.jelly

@@ -37,7 +37,7 @@ THE SOFTWARE.
       <j:set var="noPlugins"
              value="${empty(app.pluginManager.plugins) and empty(app.pluginManager.failedPlugins)}" />
 
-      <div class="jenkins-app-bar jenkins-app-bar--sticky">
+      <div class="jenkins-app-bar ${app.isQuietingDown() ? '' : 'jenkins-app-bar--sticky'}">
         <div class="jenkins-app-bar__content">
           <l:search-bar clazz="jenkins-search--app-bar"
                         placeholder="${%Search installed plugins}"

core/src/main/resources/hudson/PluginManager/updates.jelly

@@ -35,7 +35,7 @@ THE SOFTWARE.
     </l:header>
 
     <l:main-panel>
-      <div class="jenkins-app-bar jenkins-app-bar--sticky">
+      <div class="jenkins-app-bar ${app.isQuietingDown() ? '' : 'jenkins-app-bar--sticky'}" style="${app.isQuietingDown() ? 'position: static !important;' : ''}">
         <div class="jenkins-app-bar__content">
           <l:search-bar clazz="jenkins-search--app-bar"
                         placeholder="${%Search plugin updates}"