Fix references to the deprecrated admin_of field

admin/freeposte/admin/models.py

@@ -123,7 +123,7 @@ class User(Address):
         if self.global_admin:
             return Domain.query.all()
         else:
-            return self.admin_of
+            return self.manager_of
 
     def get_managed_addresses(self):
         addresses = []

admin/freeposte/admin/templates/sidebar.html

@@ -46,7 +46,7 @@
       </a>
     </li>
     {% endif %}
-    {% if current_user.admin_of or current_user.global_admin %}
+    {% if current_user.manager_of or current_user.global_admin %}
     <li>
       <a href="{{ url_for('.domain_list') }}">
         <i class="fa fa-envelope"></i> <span>Mail domains</span>