RFR 8220684 : Process.waitFor(long, TimeUnit) can return false for a process that exited within the timeout

[Ivan Gerasimov]

Hello!

The default implementation of Process.waitFor(long, TimeUnit) does not 
check if the process has exited after the last portion of the timeout 
has expired.

JDK has two implementations of Process (for Unix and Windows) and they 
both override waitFor(), so it's not an issue for them.

Still, it is better to provide a more accurate default implementation.

I'm not quite certain the regression test needs to be included in the 
fix.  The test does demonstrate the issue with the unfixed JDK and 
passed Okay on all tested platforms in Mach5.  Yet, I suspect the test 
can still show false negative results, as there are no guaranties that 
even such simple application as `true` will finish in 100 ms.
I can tag the test as @ignored with a comment, or simply remove it from 
the fix.

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8220684
WEBREV: http://cr.openjdk.java.net/~igerasim/8220684/00/webrev/

Thanks in advance for reviewing!

-- 
With kind regards,
Ivan Gerasimov