9pfs: don't use AT_EMPTY_PATH in local_set_cred_passthrough()
The name argument can never be an empty string, and dirfd always point to
the containing directory of the file name. AT_EMPTY_PATH is hence useless
here. Also it breaks build with glibc version 2.13 and older.
It is actually an oversight of a previous tentative patch to implement this
function. We can safely drop it.
Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> Signed-off-by: Greg Kurz <groug@kaod.org> Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> Reviewed-by: Eric Blake <eblake@redhat.com>