Upgrades, wrong error if there is no running nailgun

1. install 5.0
2. nailgun container was not running for some reasons (e.g. it happens if user didn't succeed to upgrade from the first time and then he wants to try again)
3. run upgrade to 5.1

Expected result:
User sees the message which is related to nailgun which is not running.

Actual result:
User sees the wrong message about died docker, in fact docker is up and running.

VERSION:
  feature_groups:
    - mirantis
  production: "docker"
  release: "5.1"
  api: "1.0"
  build_number: "503"
  build_id: "2014-09-08_00-01-11"
  astute_sha: "b622d9b36dbdd1e03b282b9ee5b7435ba649e711"
  fuellib_sha: "36ae367f521b1352b6303c6bddbe6a44519704f5"
  ostf_sha: "f7b5d9d0d1cfaba5f1fe1e2c634493e92bce11db"
  nailgun_sha: "c1ec85c185d3be1bd6c97cf1a821d1e020253a23"
  fuelmain_sha: "9978b759c7bdefff887e2ffb39588ef616b88517"