lio_listio_empty_nowait_thread sometimes does *not* hang.

The other tests consistently do hang though.

Sponsored by:	DellEMC

tests/sys/aio/lio_test.c

@@ -189,6 +189,7 @@ ATF_TC_BODY(lio_listio_empty_nowait_thread, tc)
 	struct aiocb *list = NULL;
 	struct sigevent sev;
 
+	atf_tc_skip("Sometimes hangs and sometimes passes");
 	atf_tc_expect_timeout("Bug 220398 - lio_listio(2) never sends"
 	    " asynchronous notification if nent==0");
 	ATF_REQUIRE_EQ(0, sem_init(&completions, false, 0));