iotests.py: add filter_qemu() Add a filter_qemu() helper function for replacing the QEMU program name with 'QEMU_PROG' in test's log messages. Signed-off-by: Fiona Ebner <f.ebner@proxmox.com> Message-ID: <20260930132140.2342574-3-f.ebner@proxmox.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>