RFR: 8357052: java/io/File/GetXSpace.java prints wrong values in exception

[Arno Zeller]

When the test java/io/File/GetXSpace.java fails, because the usable space is greater than the free space, the values in the exception are not the correct ones.

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Commit messages:
 - Use correct variables.

Changes: https://git.openjdk.org/jdk/pull/25250/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25250&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357052
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25250.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25250/head:pull/25250

PR: https://git.openjdk.org/jdk/pull/25250