nptl: fix sem_open with O_CREAT
Temporary file name template passed to __gen_tempname had no "XXXXXX" in it,
so __gen_tempname returned EINVAL which led to sem_open failure.
Fixes NPTL tests tst-sem4, tst-sem7, tst-sem8, tst-sem9.
Signed-off-by: Roman I Khimov <khimov@altell.ru>
Signed-off-by: Austin Foxley <austinf@cetoncorp.com>