Trying to clone a profile that includes legacy extensions results in this failure (which is buried and not properly reported, but that's a different problem):

WFLYCTL0309: Legacy extension 'org.jboss.as.web' is not supported on servers running this version. The extension is only supported for use by hosts running a previous release in a mixed-version managed domain

It's created by UnsupportedSubsystemDescribeHandler.

That failure made some sense when the only use of the 'describe' op was by an HC launching a domain server, but now 'describe' is also an impl detail of the 'clone' op, and describe may also be executed independently by users.

We need to distinguish the server launch case from other uses and only fail in the former.