In jtreg.sh it will combine all the java options and jtreg options in the `for i in "$@"` loop. SHELL use javaOpts and jtregOpts as global varable by default, this means jtreg.sh will receive the value of javaOpts and jtregOpts outside. I think this unexpected.
To avoid this siutation, I think we should unset javaOpts and jtregOpts before use it.

Below command demonstrate this bug:

> jtregOpts=-compilejdk: jtreg -compilejdk: -version
Error: Duplicate option: -compilejdk
Usage:
         jtreg options... tests...