s3:smbd/close remove filesystem lock before removing sharemode

s3:smbd/close remove filesystem lock before removing sharemode

otherwise we are open for a race condition:

opener 1 opens file and closes it
- during the close, the share mode entry will be removed from
  locking.tdb, but share mode in the file system will be dropped later
  after delete_on_close and write time updates have been done

opener 2 requests open of same file with file overwrite
- locking.tdb does not list original entry, but file system share mode
  is still around
- VFS_FTRUNCATE will fail and error was converted to STATUS_ACCESS_DENIED

Signed-off-by: Christian Ambach <ambi@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Christian Ambach <ambi@samba.org>
Autobuild-Date(master): Tue Jun 25 14:48:44 CEST 2013 on sn-devel-104