QNX: Fix MediaPlayer states handling

Task-number: QTBUG-37753
Change-Id: I61ff490f061dedd8a9bdc22d76969d9afb9a6795
Reviewed-by: Bernd Weimer <bweimer@blackberry.com>
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>