RFR (JAXP): 8068839: newDuration(x) produces incorrect outputs for some values of x

[huizhe wang]

This is a fix for an edge case. All tests passed after the fix.

JBS:
https://bugs.openjdk.java.net/browse/JDK-8068839

webrev:
http://cr.openjdk.java.net/~joehw/jdk9/8068839/webrev/

Thanks,
Joe