RFR: 8313239: InetAddress.getCanonicalHostName may return ip address if reverse lookup fails

[Jaikiran Pai]

Can I please get a review of this change which updates the javadoc of `java.net.InetAddress.getCanonicalHostName()` method to clarify its semantics? This addresses https://bugs.openjdk.org/browse/JDK-8313239.

This a javadoc only change and the documentation is updated to match the current implementation. A CSR will be drafted for this change.

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Commit messages:
 - 8313239: InetAddress.getCanonicalHostName may return ip address if reverse lookup fails

Changes: https://git.openjdk.org/jdk/pull/15134/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15134&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313239
  Stats: 20 lines in 1 file changed: 9 ins; 4 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/15134.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15134/head:pull/15134

PR: https://git.openjdk.org/jdk/pull/15134