please review: refactor test launchers to make common the building of the command

[David Hill]

Kevin, could you please review:

webrev: http://cr.openjdk.java.net/~ddhill/8147427
bug: https://bugs.openjdk.java.net/browse/JDK-8147427




-- 
David Hill<David.Hill at Oracle.com>
Java Embedded Development

"A man's feet should be planted in his country, but his eyes should survey the world."
-- George Santayana (1863 - 1952)