Actually, the failure happened with 3innodb as well. Most probably
the reason is in failing to delete a binlog file on __NT__ so that
that master increments the index of the binlog file.
The test results hide valueable warning that windows could generate
about that.

The scope of this fix is to make sure we have such warning and
to lessen chances for binlog file being held at time of closing.
The dump thread is getting a good chance to leave and 
release the file for its successful deletion.

We shall watch over the two tests as regression is not excluded.
In that case we would have an extra info possibly explaining why
__NT__ env can not close/delete the file.
However, regardless of that reason, there is alwasy workaround to mask out
non-deterministic binlog index number.