Introducing a way to control lock modes when using the NHibernate saga
persister. We're also changing the default mode from None to Upgrade since
that improves throughput when there is alot of concurrency on saga
instances. This also seems to prevent
https://nhibernate.jira.com/browse/NH-3023 from happening as well since
there will be much less rollbacks due to concurrency issues.
Closes #1342
Merge pull request #1568 from Particular/GH-1342

Introducing a way to control lock modes when using the NHibernate saga persister