[8] 8008171: Refactor KeyStore.DomainLoadStoreParameter as a standalone class

[Vincent Ryan]

Please review the following change - it's a simple re-factoring to promote a 
nested class to a stand-alone class:

Bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8008171
Webrev: http://cr.openjdk.java.net/~vinnie/8008171/webrev.00/

Thanks.