Switch default of skip-group-loading to 'true' for local auth.

The new attribute skip-group-loading was added to the local authentication definition by WFLY-3048 this needed to have a default of false for backwards compatibility purposes however in reality most would probably assume a default of true.

For WildFly 9 switch the default to true. This change in default should probably only occur if the schema version is 3 or above.

A transformer should not be required as this is not configuration that is propagated around a domain.