RFR 8160833: ClassesByName2Test.java and RedefineCrossEvent.java failing with jtreg tip

[George Triantafillou]

Please review this small change to fix test failures in two JDI tests:

JBS: https://bugs.openjdk.java.net/browse/JDK-8160833
Open webrev: http://cr.openjdk.java.net/~gtriantafill/8160833/webrev/ 
<http://cr.openjdk.java.net/%7Egtriantafill/8160833/webrev/>

Thanks to Tim Bell for his assistance.  The fix replaces the use of 
javax.rmi.CORBA.Util with String.format.  See this comment 
<https://bugs.openjdk.java.net/browse/JDK-8160833?focusedCommentId=13981130&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13981130> 
for details.

Tested locally on Linux with latest version of jtreg.

-George