xfstests: posix_memalign and io_submit do not set errno

xfstests: posix_memalign and io_submit do not set errno

posix_memalign and io_submit do not set errno, but rather return the
error respectively the negated error directly.

Found this out while figuring out why 240 reported an impossible error
from io_submit when run on NFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>