NH-941 basically working, but unnecessary updates is sent to database

The issue fixed in 3.2GA is not working entirely as expected. Foreign keys are correctly inserted, so allow null in foreign keys can be avoided, but the SQL updates is still sent to the database. It would be nice to avoid the unnecessary updates for performance reasons.

It can be tested just by profiling what is happening in the database when running the specific unit tests.I'm using SQL Server 2008 in case it should be a database specific issue.