fix for smarty security issue during ajax calls

[bucsithte]

• changed order of addTemplateDir call
• function will be now called before ajax request check
• solves issue with smarty security during ajax calls

[shopwareBot]

Hello,

thank you for creating this pull request. I have opened an issue on our Issue Tracker for you. See the issue link: https://issues.shopware.com/issues/PT-9940

Please use this issue to track the state of your pull request.

[DennisGarding]

Thank you for your contribution