Stabilize tst_QQuickPathView:dataModel()

Stabilize tst_QQuickPathView:dataModel()

- QQuickPathView::setCurrentIndex() result must be immediate
  => no need for random QTest::qWait(100) there.
- Remove another random QTest::qWait(100) after inserting
  a model item. Instead, wait for the desired result ie.
  delegate creation with QTRY_VERIFY().
- Furthermore, disable the default highlight move duration to
  avoid the auto test and QQuickPathView's internal timeline
  fighting over the current index.

Task-number: QTBUG-35705
Change-Id: Ie53fdcc8f7955a03027da38b075e6042a3aea7f2
Reviewed-by: Alan Alpert <aalpert@blackberry.com>