Process starting may not work for MySQL database

[gorbunkov]

Forum topic: https://www.cuba-platform.com/discuss/t/start-bpm-from-service-failed/8376
The problem is that MySQL has a default transaction isolation level REPEATABLE READ while most other databases use the READ COMMITTED by default. For REPEATABLE READ level an NPE may be thrown (see the project from the sample). The workaround is to change the isolation level to READ COMMITTED.