RFR: 8287104: AddressChangeListener thread inherits CCL and can cause memory leak for webapp-servers

[Jaikiran Pai]

Can I please get a review of this change which addresses https://bugs.openjdk.java.net/browse/JDK-8287104?

The change in this commit now uses an `InnocuousThread` to create a thread with `null` context classloader. The `Runnable` task of this thread just invokes a native method through JNI to be notified of IP addresses change of the host. As such any specific thread context classloader isn't necessary in this thread.

Additionally, this commit does some minor changes like making the `lock` member variable `final` and also marking the `changed` member variable as `volatile`. These changes aren't necessary for this fix, but I think would be good to have while we are changing this part of the code.

Finally, the thread that we create here, now has a specific name `Net-address-change-listener` instead of the usual system wide auto-generated name.

No new tests have been added for this change. Existing tier1, tier2 and tier3 tests have been run and no related failures have been noticed.

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Commit messages:
 - 8287104: AddressChangeListener thread inherits CCL and can cause memory leak for webapp-servers

Changes: https://git.openjdk.java.net/jdk/pull/8827/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8827&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287104
  Stats: 11 lines in 1 file changed: 5 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8827.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8827/head:pull/8827

PR: https://git.openjdk.java.net/jdk/pull/8827