title: Magento custom ACL return TRUE by default
body: <p>I have defined an acl for a tab in Manage Customer</p>
  
  <pre><code>    &lt;acl&gt;
          &lt;resources&gt;
              &lt;all&gt;
                  &lt;title&gt;Allow Everything&lt;/title&gt;
              &lt;/all&gt;
              &lt;admin&gt;
                  &lt;children&gt;
                      &lt;customer&gt;
                          &lt;children&gt;
                              &lt;manage&gt;
                                  &lt;children&gt;
                                      &lt;managepoint translate="title"&gt;
                                          &lt;title&gt;Manage Point&lt;/title&gt;
                                          &lt;sort_order&gt;100&lt;/sort_order&gt;
                                      &lt;/managepoint&gt;
                                  &lt;/children&gt;
                              &lt;/manage&gt;
                          &lt;/children&gt;
                      &lt;/customer&gt;
                  &lt;/children&gt;
              &lt;/admin&gt;
          &lt;/resources&gt;
      &lt;/acl&gt;
  </code></pre>
  
  <p>Using this code </p>
  
  <pre><code>public function canShowTab(){
      if(!Mage::getSingleton('admin/session')-&gt;isAllowed('customer/manage/managepoint'))
          return false;
      return true;
  }
  </code></pre>
  
  <p>It is expacted that by default for all users under any user role except admin role Mage::getSingleton('admin/session')->isAllowed('customer/manage/managepoint') should return FALSE but actually it returns TRUE, but if I check then uncheck this ACL for a perticular Role then ACL starts working as expected.</p>
  
  <p>Can anybody tell me why Mage::getSingleton('admin/session')->isAllowed('customer/manage/managepoint') is returning FALSE by default.</p>