The "idle-threshold" attribute is an unknown attribute when we are using a server built for "default" stability level; however the test cases added in https://issues.redhat.com/browse/WFLY-20918 feature are not prepared to handle such a situation.

To avoid explicitly ignoring them on the product branches, we should add the server setup tasks that manage the server reloading to a desired stability level, if that's possible, before ignoring the test.

See StabilityServerSetupSnapshotRestoreTasks.java