RFR: JDK-8232092 (fs) Files::isWritable returns false on a writeable root directory (win)

[Nhat Nguyen]

I'm following up on the reviewing thread here: https://mail.openjdk.java.net/pipermail/nio-dev/2020-August/007456.html

All the tests that create symlinks are now properly checked against using `TestUtil.supportsLinks`

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Commit messages:
 - Fix typo
 - 8232092: Files::isWritable returns false on a writeable root directory (win)

Changes: https://git.openjdk.java.net/jdk/pull/287/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=287&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8232092
  Stats: 495 lines in 3 files changed: 493 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/287.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/287/head:pull/287

PR: https://git.openjdk.java.net/jdk/pull/287