qemu_driver: unlink new domain cfg file when rollback
If we failed to unlink old dom cfg file, we goto rollback.
But inside rollback, we fogot to unlink the new dom cfg file.
This patch fixes this issue.
Signed-off-by: Chen Hanxiao <chenhanxiao@gmail.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>