RFR 8061448, Update sun/misc/JarIndex tests to cleanup the check for the "jre" directory

[FELIX YANG]

Hi all,
   please review the fix for 8061448. It cleans up dependency with 
"jre" directory and tools.jar, which have been removed by Jigsaw feature.

Bug:
    https://bugs.openjdk.java.net/browse/JDK-8061448
Webrev:
    http://cr.openjdk.java.net/~xiaofeya/8061448/webrev.00/

I needs a sponsor for this change.

Thanks,
Felix