RFR 8159034: 4 nashorn ant tests fail with latest jdk9-dev build with IncompatibleClassChangeError

[Sundararajan Athijegannathan]

Please review http://cr.openjdk.java.net/~sundar/8159034/webrev.00/ for
https://bugs.openjdk.java.net/browse/JDK-8159034

No new regression test added as there are already tests cover calling
inherited default methods on interfaces.

Thanks,

-Sundar