Backport of 8077608

[Stuart Monteith]

Hello,
    The fix in 8077608 was never backported to jdk8u. There are a
number of testcases that spawn their own java processes that then fail
to run as they do not have the correct classpath when run under JTReg
with "-agentvm".

The patch for jdk9 applies almost cleanly to jdk8u:

]http://mail.openjdk.java.net/pipermail/hotspot-dev/2015-April/017937.html
https://bugs.openjdk.java.net/browse/JDK-8077608
http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/af2a1e9f08f3

Is there any reason why this wasn't backported? If need be, I can
produce test and make a patch available.

BR,
   Stuart