Fix bugs in Ansible playbook that caused `make dev-go` to fail
Fix bugs in Ansible playbook that caused `make dev-go` to fail

- When the grsec kernel is not present, the previous logic caused
  a default Node image (without the custom CI Dockerfile) to be
  used. As a result, `npm install` would fail (due to missing
  `python` and `g++` dependencies) and `make dev-go` would time
  out at this stage.

- The SHA-256 hash was not appended to the name of the Django
  image. Once the bug above was fixed, this caused Docker to
  look for an image called `stn_django:latest` (`latest` is the
  default tag). Since that image does not exist, it would fail
  at this stage.

freedomofpress/securethenews,freedomofpress/securethenews,freedomofpress/securethenews,freedomofpress/securethenews