Close connection on session consistency loss by default

[achamayou]

#4595 introduced error messages on session consistency breaks, followed by a session closure. Sessions can be long lived however, and users may not require session consistency (either because the application is idempotent, or because they check commit explicitly anyway).

In those cases, they would prefer an early session closure, resulting in one less (potentially confusing when it's delayed) error message.

Based on this feedback, I think we should at least change the default behaviour, and perhaps make this configurable.