RFR(XS): 8252804: [test] Fix 'ReleaseDeflater.java' test after downport of 8234011

[Volker Simonis]

Hi,

can I please have a review for this trivial test fix which was
introduced with the downport of "JDK-8234011: (zipfs) Memory leak in
ZipFileSystem.releaseDeflater()" [1]. The downport [2] contained the
test "test/jdk/jdk/nio/zipfs/ReleaseDeflater.java" which had to be
slightly modified for the downport. These modifications made him fail
on Windows.

http://cr.openjdk.java.net/~simonis/webrevs/2020/8252804
https://bugs.openjdk.java.net/browse/JDK-8252804

Do you want me to bring this to 11.0.9 with a "jdk11u-critical-request"?

Thank you and best regards,
Volker

[1] https://hg.openjdk.java.net/jdk/jdk/rev/fe87a92570db
[2] https://hg.openjdk.java.net/jdk-updates/jdk11u-dev/rev/cb299db4a569