Reactivate integration tests for core-sync

[ursjoss]

In the context of running postgresql in a docker container for jOOQ code generation and for integration tests (#88), I had to disable the integration tests for public-web.

I renamed the path for the respective test-set from core/sync/src/intTest to core/sync/intTestDisabled.

The problem in particular is that we need to databases with three datasources to test the persistence layer involving batch, core and public database (with batch on core).

Find a way to reactivate those tests.