Correct DateField smoke test: use explicit locale.

uitest/src/main/java/com/vaadin/tests/smoke/DateFieldSmoke.java

@@ -35,6 +35,8 @@ public class DateFieldSmoke extends AbstractTestUIWithLog {
 
     @Override
     protected void setup(VaadinRequest request) {
+        setLocale(Locale.ENGLISH);
+
         InlineDateField inline = new InlineDateField();
         PopupDateField popup = new PopupDateField();
 
@@ -42,6 +44,9 @@ public class DateFieldSmoke extends AbstractTestUIWithLog {
         popup.setValue(new Date(year, 11, 28));
         inline.setValue(new Date(year, 11, 29));
 
+        popup.setDateFormat("MM/dd/yy");
+        inline.setDateFormat("MM/dd/yy");
+
         popup.addValueChangeListener(event -> log(
                 "Popup value is : " + FORMAT.format(popup.getValue())));
         inline.addValueChangeListener(event -> log(