test-utimens: avoid spurious failure

test-utimens: avoid spurious failure

Fixes a spurious failure on ext3, with one-second resolution,
now that ctime effects are being tested for inequality.

* tests/test-chown.h (nap): Factor...
* tests/nap.h: ...into new file.
* tests/test-lchown.h (nap): Avoid duplication.
* tests/test-utimens-common.h (nap): Use shared implementation,
necessary on file systems with 1-second resolution.
* modules/chown-tests (Files): Include new file.
* modules/fdutimensat-tests (Files): Likewise.
* modules/futimens-tests (Files): Likewise.
* modules/lchown-tests (Files): Likewise.
* modules/openat-tests (Files): Likewise.
* modules/utimens-tests (Files): Likewise.
* modules/utimensat-tests (Files): Likewise.

Signed-off-by: Eric Blake <ebb9@byu.net>