r9584: Fix a race condition in Samba 3. If two files are opened simultaneously with

r9584: Fix a race condition in Samba 3. If two files are opened simultaneously with
NTCREATEX_DISP_CREATE (create if not exists, else fail) they might end up with
two or more times NT_STATUS_OK as EEXIST is not correctly handled.

Jeremy, please look closely at this. You can easily verify this by adding a
smb_msleep(100) to the top of open_file_ntcreate and run the new samba4
torture test. It does also happen without the msleep, but not as reliably.

Thanks,

Volker
(This used to be commit c803d4c9a588e39a90ddfe900be9b9de1a861f82)