sem_clockwait_np test: fix usage of ATF API

ATF_REQUIRE_ERRNO requires the given errno iff the given expression is
true. These test cases used it incorrectly, potentially allowing
sem_clockwait_np to succeed when it was expected to fail. Use separate
ATF calls to require failure and the expected errno.

MFC after: 1 week
Sponsored by: Dell EMC Isilon