Configurable image

[pb82]

Make the Grafana Image and Tag configurable using command line args.

Verification:

1. Create an empty namespace using grafana
2. Run the operator locally using operator-sdk up local --namespace=grafana --operator-flags "--grafana-image registry.redhat.io/openshift3/grafana --grafana-image-tag v3.11"
3. Deploy a grafana instance to this namespace using oc create -f deploy/examples/Grafana.yaml
4. Wait until everything is deployed.
5. Inspect the Grafana deployment and make sure it is using the specified Red Hat image.
6. Delete the Grafana CR and restart the operator without the extra flags
7. Deploy another Grafana instance
8. Make sure that this time it is using the public community Grafana image.

[davidkirwan]

After removing the Grafana CR and restarting the operator without the custom flags

[davidkirwan]

LGTM

[david-martin]

@pb82 @davidkirwan I'm interested in your thoughts on changing how the custom image is specified.
The approach in this PR looks reasonable, however it has a couple of limitations.

• It isn't possible to change the base image per Grafana instance (minor)
• The application-monitoring-operator has the image to use baked in use red hat grafana image integr8ly/application-monitoring-operator#31. This means the application-monitoring-operator cannot be for community use.

The prometheus operator allows the base image to be specified in the CR here: https://github.com/coreos/prometheus-operator/blob/master/pkg/apis/monitoring/v1/types.go#L104-L105.
What are your thoughts on moving to a similar approach for specifying the Grafana image to use?