tsan: fix another false positive related to open/close

The false positive fixed by commit f831d6fc
("tsan: fix false positive during fd close") still happens episodically
on the added more stressful test which does just open/close.

I don't have a coherent explanation as to what exactly happens
but the fix fixes the false positive on this test as well.
The issue may be related to lost writes during asynchronous MADV_DONTNEED.
I've debugged similar unexplainable false positive related to freed and
reused memory and at the time the only possible explanation I found is that
an asynchronous MADV_DONTNEED may lead to lost writes. That's why commit
302ec7b9 ("tsan: add memory_limit_mb flag") added StopTheWorld around
the memory flush, but unfortunately the commit does not capture these findings.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D121363