ivi-shell: Fix resource leak.

I think there is a bug.
surface_destroy() needs to call wl_resource_destroy(resource).
wl_resource_destroy() will internally as the last thing call the
destructor function you set with wl_resource_set_implementation(), which
means that shell_destroy_shell_surface() will get called when you call
wl_resource_destroy().

Signed-off-by: Nobuhiko Tanibata <NOBUHIKO_TANIBATA@xddp.denso.co.jp>