DERBY-553: With JDK 1.5 signatures from signed jar in a database are not returned by Class.getSigners() when database in stored in a jar file.

Enable test case that fails because of this bug, on the platforms where it is fixed.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1437359 13f79535-47bb-0310-9956-ffa450edef68