sysroot: Close sysroot fd in finalize

Just noticed this while I was going to add another one there.

src/libostree/ostree-sysroot.c

@@ -66,6 +66,9 @@ ostree_sysroot_finalize (GObject *object)
   g_clear_object (&self->sepolicy);
   g_clear_object (&self->repo);
 
+  if (self->sysroot_fd != -1)
+    (void) close (self->sysroot_fd);
+
   G_OBJECT_CLASS (ostree_sysroot_parent_class)->finalize (object);
 }