Fix the default constructor test case

Commit 7c737e0edcb93585856c65890ef34e5c5a28ee6b introduced
this regression by changing the default baud rate from 0 to 9600.

Change-Id: If20315eb53c3416646541dda82add0f4fc12d4a3
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Laszlo Papp <lpapp@kde.org>