Postgres is now fixed.  When an exception is raised, the database
handle is invalid and select/update etc. raise an exception.
Performing a fixup requires the ability to select from the
database. Now the database is committed after each row and on
exception, the database is rolled back.

For other rdbms backends, the methods that commit/rollback are
no-ops.

Mysql is fixed so that the index that makes sure a class's key is
unique is added.

The the roundup database version for rdbms backends is now
version 6.  Admins need to do a 'roundup-admin migrate' as part
of this deployment.  Only mysql gets a schema change to
add the index that makes sure that the class's key is unique.

memorydb skips the test similar to anydbm since it never had the issue.

changeset:   6433:c1d3fbcdbfbd - version upgrade 5->6,
             constraint added to mysql, postgresql fixes.
changeset:   6434:269f39e28d5c - changes to testing


see upgrading.txt doc and checkin notes for more info.