ERP5TypeFunctionalTestCase: make sure to always quit browser

This is important to release the session on selenium server

product/ERP5Type/tests/ERP5TypeFunctionalTestCase.py

@@ -209,9 +209,9 @@ class FunctionalTestRunner:
       ).encode('UTF-8'),
         html_parser
       )
-      browser.quit()
     finally:
       xvfb.quit()
+      browser.quit()
     return iframe
 
   def processResult(self, iframe):