RFR: 8307887: (fs) Files.createSymbolicLink throws less specific exception when in developer mode and file already exists

[Brian Burkhalter]

If the second attempt to create the link fails, throw the exception referring to the last error if it is anything other than due to lack of link creation privilege or failure to recognize the flag for unprivileged link creation.

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Commit messages:
 - 8307887: Excise trailing whitespace
 - 8307887: (fs) Files.createSymbolicLink throws less specific exception when in developer mode and file already exists

Changes: https://git.openjdk.org/jdk/pull/14255/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14255&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307887
  Stats: 26 lines in 2 files changed: 20 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/14255.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14255/head:pull/14255

PR: https://git.openjdk.org/jdk/pull/14255