Consider switching default cache configuration for distributed web session to use non-tx cache

Since [1], we no longer require transactions to ensure safe/consistent access/modification to mutable session attributes by concurrent requests for a given session.  Therefore, we can now change the default cache configuration for web session to be non-transactional, to be more in line with the session access characteristics expected by modern web applications (and the majority of users).

[1] https://issues.redhat.com/browse/WFLY-13998