usleep: use it to simplify tests

usleep: use it to simplify tests

Blindly using usleep makes it easier to write tests.

* modules/stat-time-tests (Depends-on): Add usleep.
(configure.ac): Drop usleep check.
* modules/chown-tests (Depends-on, configure.ac): Likewise.
* modules/lchown-tests (Depends-on, configure.ac): Likewise.
* modules/fdutimensat-tests (Depends-on, configure.ac): Likewise.
* modules/futimens-tests (Depends-on, configure.ac): Likewise.
* modules/openat-tests (Depends-on, configure.ac): Likewise.
* modules/utimens-tests (Depends-on, configure.ac): Likewise.
* modules/utimensat-tests (Depends-on, configure.ac): Likewise.
* modules/pipe-filter-gi-tests (Depends-on, configure.ac):
Likewise.
* tests/test-chown.h (nap): Rely on nicer usleep semantics.
* tests/test-lchown.h (nap): Likewise.
* tests/test-pipe-filter-gi2-main.c (small_nap): Likewise.
* tests/test-stat-time.c (nap): Likewise.
* tests/test-utimens-common.h (nap): Update comments.

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