Usage of wildfly.sasl.local-user.default-user in core configuration files

The property wildfly.sasl.local-user.default-user is present in some, commented out on other, and absent from some default configuation files in core. (the default host-slave.xml for example has it, but it appears to have no effect if removed). There is uneven usage of it throughout the testsuite config files.

We should review and make the usage (or non-usage) consistent.