[FIX] correct a layout issue in viewmanager (webclient)

problem was that the pager was not displayed/hidden at the correct moment
Result is that when switching views, the header sometimes takes an extra
line.  The pager is now hidden just before creating the view

addons/web/static/src/js/views.js

@@ -715,6 +715,7 @@ instance.web.ViewManager =  instance.web.Widget.extend({
         controller.on('view_loaded', this, function () {
             view_loaded.resolve();
         });
+        this.$('.oe-view-manager-pager > span').hide();
         return $.when(controller.appendTo($container), view_loaded)
                 .done(function () { 
                     self.trigger("controller_inited", view.type, controller);

addons/web/static/src/xml/base.xml

@@ -568,7 +568,7 @@
         </table>
     </div>
 </t>
-<div t-name="ViewPager">
+<span t-name="ViewPager">
     <div class="oe_pager_value">
         <t t-raw="0"/>
     </div>
@@ -576,7 +576,7 @@
         <a class="fa fa-chevron-left btn btn-default oe-pager-button" type="button" data-pager-action="previous"></a>
         <a class="fa fa-chevron-right btn btn-default oe-pager-button" type="button" data-pager-action="next"></a>
     </div>
-</div>
+</span>
 
 <div t-name="Sidebar" class="oe_sidebar btn-group">
     <t t-foreach="widget.sections" t-as="section">