tests: Mark tests that fail on NetBSD as expected failures. * modules/dup3-tests (Depends-on): Add test-xfail. (Makefile.am): Expect that test-dup3 fails on NetBSD. * modules/fdutimensat-tests (Depends-on): Add test-xfail. (Makefile.am): Expect that test-fdutimensat fails on NetBSD. * modules/futimens-tests (Depends-on): Add test-xfail. (Makefile.am): Expect that test-futimens fails on NetBSD. * modules/utimens-tests (Depends-on): Add test-xfail. (Makefile.am): Expect that test-utimens fails on NetBSD. * modules/utimensat-tests (Depends-on): Add test-xfail. (Makefile.am): Expect that test-utimensat fails on NetBSD.