[8u] RFR: Backport of 8067796 (process) Process.waitFor(timeout, unit) doesn't throw NPE if timeout is less than, or equal to zero when unit == null

[Sergey Nazarkin]

Hi!

Please review backport of the fix [1] for the issue [2]. The fix was originally made for jdk9 and included into oracle u251. It’s not applied cleanly due to file difference. 

Created ambrella case for the backport [3]

[1] http://cr.openjdk.java.net/~snazarki/8241535/
[2] https://bugs.openjdk.java.net/browse/JDK-8067796
[3] https://bugs.openjdk.java.net/browse/JDK-8241535