Respect JSON CLI switch on failed job creations

When we run `helios create --json ...`, we returned this:

  Failed: JobDeployResponse{status=JOB_ALREADY_EXISTS}

Let's return this:

  {"errors":[],"id":"foo-service:0.0.8:6a0","status":"JOB_ALREADY_EXISTS"}

So that users can parse the response.
Merge pull request #147 from spotify/dxia/output-json-on-job-creation-fail

Respect JSON CLI switch on failed job creations