JDK 9 RFR of JDK-8169971: tools/jlink/multireleasejar/JLinkMultiReleaseJarTest.java fails intermittently

[Chris Hegarty]

> On 12 Apr 2017, at 17:36, Paul Sandoz <paul.sandoz at oracle.com> wrote:
> ..
> Do you think it’s simpler just to let jtreg cleanup? There are a few Mr.Jar tests that clean up after themselves but i wonder if it’s just simpler to let jtreg do it? any thoughts on that?

I added these test library utility methods. Some times you actually
need to clean up, other times you can leave it to jtreg ( if the files
are all within the working/scratch directory ). Jtreg has similar
retry logic when deleting files on Windows.

It is common to see tests cleanup after themselves, as the original
author may have been running the test standalone, not in jtreg,
but we're mostly past that now. 

In this particular case it may be ok to leave it to jtreg to do the
clean up.

-Chris.