fix 11465: restrictions one changes to user, group

To test, work with SQL to make sure that you cannot rename the `root`, `guest` users, nor the `system`, `user`, `guest` groups, nor can you remove the `root` user from the `system` or `user` groups. Also test that other changes on those tables -- updates, deletes -- remain permitted.

Also, check that http://hudson.openmicroscopy.org.uk/job/OmeroJava-integration-develop/lastCompletedBuild/testngreports/integration/integration.AdminServiceTest/ continues to pass.