set_igvm allocates filename via g_strdup, but igvm_cfg_finalize
did not free it.
Fixes: c1d466d267 ("backends/igvm: Add IGVM loader and configuration")
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>