RFR(S) : 8073159 : improve Test6857159.java

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev/8073159/webrev.00/
> 57 lines changed: 1 ins; 54 del; 2 mod;

Hi all,

could you please review this fix for test/compiler/c2/6857159/Test6857159.java?
the test was ported to java-only by JDK-8068440, but java implementation doesn’t pass exernal vm flags to a child process and doesn’t check that this process exists gracefully. the changeset fixes that and also removes shell-file which is unneeded after JDK-8068440.

JBS: https://bugs.openjdk.java.net/browse/JDK-8073159
webrev: http://cr.openjdk.java.net/~iignatyev/8073159/webrev.00/

Thanks,
— Igor