ISPN-3996 LocalCachePerformantConfTest is reusing the same file path for...

... multiple tests

On IRC we said this should use TestingUtil.tmpDirectory(), but it actually turns out that:
 - each of the ten tests are using the same configuration
 - the purpose of the test is to verify behaviour in context of an XML parsed configuration

So I just separated the configuration file to use a different hard-coded path compared to the (single) other test using this configuration.