the upper limit of total rollback segments from 256 to 128. This is because
we can't use the sign bit. It has not caused problems in the past because we
only created one segment. InnoDB has always had the capability to use the
additional rollback segments therefore this patch is backwards compatible.
The only requirement to maintain backward compatibility has been to ensure
that the additional segments are created after the double write buffer.
This is to avoid breaking assumptions in the existing code.

Fix Bug#26590 MySQL does not allow more than 1023 open transactions