RFR 8190698: jjs tool of jdk.scripting.nashorn.shell module should not statically depend on java.desktop

[Sundararajan Athijegannathan]

Please review.

Bug: https://bugs.openjdk.java.net/browse/JDK-8190698
Webrev: http://cr.openjdk.java.net/~sundar/8190698/webrev.00

Thanks,
-Sundar