Get integration tests running in CI

@3c2b2ff5 contrinubted a samba integration test script but it needs a bit of work to run in Travis CI. I'd also like to turn my (not submitted) OpenLDAP test script into an integration test.

So two goals:

- make the integration tests runnable manually
- incorporate the tests on CI. We don't have to keep Travis if, say, spinning up a docker container on Circle to run the source server is significantly easier.