RFR: 8287580: (se) CancelledKeyException during channel registration

[Brian Burkhalter]

Ignore `CancelledKeyException` during registration.

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Commit messages:
 - 8287580: (se) CancelledKeyException during channel registration

Changes: https://git.openjdk.java.net/jdk/pull/8978/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8978&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287580
  Stats: 83 lines in 2 files changed: 83 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8978.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8978/head:pull/8978

PR: https://git.openjdk.java.net/jdk/pull/8978