RFR: 8291760: PipelineLeaksFD.java still fails: More or fewer pipes than expected [v4]

[Roger Riggs]

> Revised test to check and close all of the streams used in the pipeline.
> 
> The test now checks the content length and closes each stdout and stderr stream.
> 
> The previous technique to redirect stderr to stdout was ineffective because the fd/stream was still created in the parent process.  Created [8291986](https://bugs.openjdk.org/browse/JDK-8291986) ProcessBuilder.redirectErrorStream(true) leaves error stream available to investigate

Roger Riggs has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge branch 'master' into 8291760-leaks-close
 - Revised test to read, check, and close streams from all processes in the pipeline.
   If any unexpected output is found it is printed.
 - Merge branch 'master' into 8291760-leaks-close
 - 8291760: PipelineLeaksFD.java still fails: More or fewer pipes than expected
   Check the contents and close each stdout and stderr stream.

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Changes: https://git.openjdk.org/jdk/pull/9905/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9905&range=03
  Stats: 28 lines in 2 files changed: 8 ins; 7 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/9905.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9905/head:pull/9905

PR: https://git.openjdk.org/jdk/pull/9905