[test] for coreNLP: allow to use the already started corenlp

Thing is: I sometimes have corenlp/postgres running for my dev
env. When I start tests, they fail because they try to start corenlp
again on the same port. So what I added was checking for that "address
already in use" condition and going on with the tests. CoreNLP is
stateless so it shouldn't matter which one we use for tests.