hg: code-tools/jtreg: Set FS, PS, NULL for shell tests

[jonathan.gibbons at oracle.com]

Changeset: b4ec8b1f32b4
Author:    jjg
Date:      2019-01-25 12:02 -0800
URL:       http://hg.openjdk.java.net/code-tools/jtreg/rev/b4ec8b1f32b4

Set FS, PS, NULL for shell tests

! src/share/classes/com/sun/javatest/regtest/exec/ShellAction.java
! src/share/doc/javatest/regtest/tag-spec.html
! test/rerun/std/ShellTest.agentvm.out
! test/rerun/std/ShellTest.othervm.out