MAGETWO-53299: "Go Today" button is not working for dates range component

- added getTimezoneDate method for backward compatibility

Author: iivashchenko

lib/web/mage/calendar.js

@@ -388,6 +388,15 @@
         _destroy: function () {
             this.element[this._picker()]('destroy');
             this._super();
+        },
+
+        /**
+         * Method is kept for backward compatibility and unit-tests acceptance
+         * see \mage\calendar\calendar-test.js
+         * @return {Object} date
+         */
+        getTimezoneDate: function () {
+            return this._getTimezoneDate();
         }
     });