[FIX] web_kanban: remove add new column on 'Discard'

The 'Add New Column' was still in `folded` mode after clicking on 'Discard'
because the mode was toggle two times: one by `_cancel` and another one by
`_onClick` which already toggles the mode.

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

@@ -184,14 +184,6 @@ var ColumnQuickCreate = AbstractQuickCreate.extend({
     // Private
     //--------------------------------------------------------------------------
 
-    /**
-     * @override
-     * @private
-     */
-    _cancel: function () {
-        this.folded = true;
-        this._update();
-    },
     /**
      * Triggers up an event to quick create a column with the given value
      *

addons/web/static/tests/views/kanban_tests.js

@@ -587,7 +587,7 @@ QUnit.module('Views', {
     });
 
     QUnit.test('create a column in grouped on m2o', function (assert) {
-        assert.expect(10);
+        assert.expect(12);
 
         var nbRPCs = 0;
         var kanban = createView({
@@ -615,6 +615,15 @@ QUnit.module('Views', {
 
         kanban.$('.o_column_quick_create').click();
 
+        assert.ok(kanban.$('.o_column_quick_create input').is(':visible'),
+            "the input should be visible");
+
+        // discard the column creation and click it again
+        kanban.$('.o_column_quick_create .o_kanban_cancel').click();
+        assert.notOk(kanban.$('.o_column_quick_create input').is(':visible'),
+            "the input should not be visible after discard");
+
+        kanban.$('.o_column_quick_create').click();
         assert.ok(kanban.$('.o_column_quick_create input').is(':visible'),
             "the input should be visible");