RFR (xs) 8172246: [TESTBUG] runtime/RedefineTests/RedefinePreviousVersions.java 'Class unloading: has_previous_vers,ions = true' missing from stdout/stderr

[Coleen Phillimore]

Summary: add boolean to gate redefinition start

open webrev at http://cr.openjdk.java.net/~coleenp/8172246/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8172246

Tested multiple times with new better test code.

Thanks,
Coleen