Fixed some accessibility issues:

1) Added missing search filter label in backgrid.
  2) broken aria issue for objects menu.

web/pgadmin/browser/static/js/browser.js

@@ -372,7 +372,7 @@ define('pgadmin.browser', [
         // Create a dummy 'no object seleted' menu
         var create_submenu = pgAdmin.Browser.MenuGroup(
           obj.menu_categories['create'], [{
-            $el: $('<li><a class="dropdown-item disabled" href="#">' + gettext('No object selected') + '</a></li>'),
+            $el: $('<li><a class="dropdown-item disabled" href="#" role="menuitem">' + gettext('No object selected') + '</a></li>'),
             priority: 1,
             category: 'create',
             update: function() {},

web/pgadmin/static/js/backgrid.pgadmin.js

@@ -1957,6 +1957,10 @@ define([
    */
   Backgrid.Extension.ClientSideFilter = Backgrid.Extension.ClientSideFilter.extend({
     $customSearchBox: null,
+    template: function (data) {
+      return '<span class="search">&nbsp;</span><input type="search" ' + (data.placeholder ? 'aria-label= "' + data.placeholder + '"' : '')+' '+ (data.placeholder ? 'placeholder="' +
+      data.placeholder + '"' : '') + ' name="' + data.name + '" ' + (data.value ? 'value="' + data.value + '"' : '') + '/><a class="clear" data-backgrid-action="clear" href="#">&times;</a>';
+    },
 
     searchBox: function() {
       if(this.$customSearchBox) {