Disable Integration Test 525 for S3

This disabled the integration test 525 (*Split a Huge Repository into Nested Catalogs*) for the S3 tests. It takes forever with the current test setup and is intended to test the nested catalog handling anyway.
In any case, I need to revise the S3 tests at some point, as they are only run on SLC6 x64 and utilise a pretty simple configuration. Then we might opt to switch it on again. At the moment is just slows down test cycles too much.