tests/qtest: Delete previous boot file

A test run may create boot files several times. Delete the previous boot
file before creating a new one.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20240823-san-v4-7-a24c6dfa4ceb@daynix.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
1 file changed