[4/4] ntdll: Properly set flag which indicates buffer empty state.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
http://testbot.winehq.org/JobDetails.pl?Key=26878

Your paranoid android.


=== WVISTAX64 (32 bit comm) ===
comm.c:835: Test failed: WriteFile took 16 ms to write 0 Bytes at 150 Baud
comm.c:1443: test_AbortWaitCts timeout 500 handle 000000B4
comm.c:1410:  Changing CommMask on the fly for handle 000000B4 after timeout 500