DERBY-6017: IN lists with mixed types may return wrong results

Make the test check numeric values rather than the string
representation of the values. This should make the test less likely
to fail if the string representation of floating point numbers is
different on a platform.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1450695 13f79535-47bb-0310-9956-ffa450edef68