tests: Port closure-refcount from g_thread_create() to g_thread_new()
tests: Port closure-refcount from g_thread_create() to g_thread_new()

g_thread_create() has been deprecated for a long time.

Signed-off-by: Philip Withnall <29c2a2ac2a854b9cf047275aa9de346d096be2e0@endlessm.com>

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib