8216134 (process) ProcessBuilder startPipeline does not hide piped streams

[Roger Riggs]

Please review a bug fix for the ProcessBuilder startPipeline test and 
Windows implementation.
The test failed to check that Process.getInputStream returned the null 
stream
for all but the last process in the pipeline.  When the test was fixed 
it failed on Windows.
The Windows ProcessImpl did not ensure that getInputStream returned a 
null stream.

The same issue was found and fixed in the AIX implementation (JDK-8211844)
which prompted investigation of the test.

Webrev:
  http://cr.openjdk.java.net/~rriggs/webrev-pipeline-8211844/

Happy New Year!  Roger