if nothing was added to the log
(BUG#34712 maria_read_log changes log
file content on several platforms though not needed)
Fixed callback call (now under loghandler lock).


storage/maria/ma_loghandler.c:
  Flag that signaling about "everythig-flushed" state of
  the log added, to avoid changing log on flush request
  if nothing was written but horizon placed on the page boarder.
  Fixed callback call (now under loghandler lock).