Readd static resource path for task icons [JENKINS-24316]

Missed this in previous commit - bad idea making even small changes late at night ;)

(cherry picked from commit 3daa6a97b0)

core/src/main/resources/lib/layout/task.jelly

@@ -116,7 +116,7 @@ THE SOFTWARE.
       <j:if test="${!icon.startsWith('/')}">
         <j:set var="icon" value="/${icon}"/>
       </j:if>
-      <j:set var="icon" value="${rootURL}${icon.startsWith('images/') || icon.startsWith('plugin/') ? h.resourcePath : ''}${icon}"/>
+      <j:set var="icon" value="${rootURL}${icon.startsWith('/images/') || icon.startsWith('/plugin/') ? h.resourcePath : ''}${icon}"/>
       <j:when test="${enabled==false}">
         <div class="task disabled">
           <span>