RFR: 8291911: java/io/File/GetXSpace.java fails with "53687091200 != 161051996160"

[Brian Burkhalter]

On Windows, suppress failure if the total space indicated by `df` is less than `FileStore::getTotalSpace` and the free space indicated by `df` equals `FileStore::getUnallocatedSpace`.

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Commit messages:
 - 8291911: java/io/File/GetXSpace.java fails with "53687091200 != 161051996160"

Changes: https://git.openjdk.org/jdk/pull/9856/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9856&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291911
  Stats: 8 lines in 2 files changed: 5 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9856.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9856/head:pull/9856

PR: https://git.openjdk.org/jdk/pull/9856