Merge: Ci: move services to specific hostnames

Testing nit with various services is a PITA.

The previous solution was to test them on localhost and requires that the services are available and configured on each test node (it is not always as easy as it seems).
Another problem with `localhost` is that testing within docker is complex as running multiple services in a single container is discouraged.

Here, we propose to simply move the service from localhost to specific hostnames.
This is to be the current "good" practice and is supported out-of-the-box bu various CI infrastructure including gitlab-ci.

Pull-Request: #2737

diff --cc .gitlab-ci.yml
Simple merge

diff --cc lib/neo4j/neo4j.nit
Simple merge

diff --cc misc/docker/ci/Dockerfile
Simple merge

diff --cc tests/gitlab_ci.skip
index 8467aad,5d4f23a..c75645c
--- 1/tests/gitlab_ci.skip
--- 2/tests/gitlab_ci.skip
+++ b/tests/gitlab_ci.skip
@@@ -1,10 -1,9 +1,6 @@@
  emscripten
  java
  glsl
- mongo
  mpi
- neo
  objc
- postgres
- nitrpg
 -action_nitro
 -asteronits
  wiringPi