RFR: 8293696: java/nio/channels/DatagramChannel/SelectWhenRefused.java fails with "Unexpected wakeup" [v6]

[Darragh Clarke]

> Added logging to SelectWhenRefused for an intermittent failure caused by unexpected wakeups, this includes trying to receive data if there is any available to identify where it is coming from.
> 
> I also set the test to run in othervm mode which should reduce the chances of this failure happening in the first place.

Darragh Clarke has updated the pull request incrementally with one additional commit since the last revision:

  fixed buffer output

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10851/files
  - new: https://git.openjdk.org/jdk/pull/10851/files/3099caa8..43277609

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10851&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10851&range=04-05

  Stats: 13 lines in 1 file changed: 7 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/10851.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10851/head:pull/10851

PR: https://git.openjdk.org/jdk/pull/10851