Removal of "latest" tag from Docker images

In order to avoid bad surprises when new (incompatible) versions of Graylog are released, we decided to remove the “latest” tag from our graylog/graylog (same as graylog2/graylog) Docker image.

If you’re using either graylog/graylog or graylog2/graylog to run Graylog in Docker (or Kubernetes), please make sure to specify at least the minor version (i. e. graylog/graylog:2.4) or the fully qualified version (i.e. graylog/graylog:2.4-3-1) of the Docker image.

Please refer to the following GitHub issue for the rationale behind that decision: