fix: travis-ci error - back to trusty with explicit db service
fix: travis-ci error - back to trusty with explicit db service

  - travis have been moving builds from trusty to xenial
  - when planner is tested on Xenial it fails. Because:
    - 1. no postgresql service
      - could not connect to server: Connection refused
        Is the server running on host "localhost" (127.0.0.1) and
        accepting TCP/IP connections on port 5432?
    - 2. tests become 'flaky'
  - setting back to trusty and adding explicit postgres service

despo/planner,despo/planner,laszpio/planner,laszpio/planner,codebar/planner,codebar/planner,despo/planner,laszpio/planner,codebar/planner,codebar/planner,laszpio/planner,despo/planner