java-idp-jetty-base: persistTempDirectory in idp.xml for Jetty 12

[Cantor, Scott]

> I am not on 12 yet so I have no experience to say.

Playing with it myself, yeah, it's not cleaning up. I suspect it's a bug, but will have to dig into the code to see what new settings might exist.

Rod mentioned to me that I guess this has been broken on Windows all along.

Certainly is disappointing, this is the sort of thing that led to us dropping Tomcat. I will at least say it's not apparently reusing the older folder, which Tomcat does, catastrophically.

-- Scott