Revert "Webadmin: set default single Qxl device to true"

This reverts commit c79a4ba6cc6a2b8c15e351d6c14c804ea59ff703.
since it breaks unit tests

Change-Id: I364799238f45a738b777028fd10ff1236b51d8eb
Signed-off-by: Omer Frenkel <ofrenkel@redhat.com>