RFR: 8307976: (fs) Files.createDirectories(dir) returns dir::toAbsolutePath instead of dir

[Brian Burkhalter]

Return `dir`, not `dir::toAbsolutePath`.

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Commit messages:
 - 8307976: (fs) Files.createDirectories(dir) returns dir::toAbsolutePath instead of dir

Changes: https://git.openjdk.org/jdk/pull/13959/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13959&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307976
  Stats: 15 lines in 2 files changed: 9 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/13959.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13959/head:pull/13959

PR: https://git.openjdk.org/jdk/pull/13959