Coverity spotted a double-free (CID 1508254); we g_string_free(path) and
then for some reason immediately call free(path) too.
We should just use g_autoptr() for it anyway, which simplifies the code
a bit.
Fixes: 7a8a749da7d3 ("hw/xen: Move xenstore_store_pv_console_info to xen_console.c")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>