backends/igvm-cfg: free filename on finalization

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>

backends/igvm-cfg.c

@@ -108,4 +108,5 @@ static void igvm_cfg_finalize(Object *obj)
     if (igvm->file >= 0) {
         igvm_free(igvm->file);
     }
+    g_free(igvm->filename);
 }