Clustering TS: Running a single test with -Dtest= can only be used with main tests

Related to WFLY-13563.

The -Dtest=foo will only run if the test foo is part of the main surefire execution. e.g. running a single node test will try to run that test in the main execution and would fail.

Unfortunately, the -Dtest overrides includes/excludes fo the surefire plugin execution, which does not work for us well.

Document how profile selection introduced in WFLY-13557 could be used to run single test.