Make template imagePullSecrets optional

[fgharo]

When deploying fake-gpu-operator onto Openshift 4.20 the following warning events occur:

Unable to retrieve some image pull secrets (gcr-secret); attempting to pull the image may not succeed.

The operator still succeeds at pulling the container images so these events seem to be noise.

Can we make these references optional in the templates? Let me know if so, I can offer some time to change them.

$ grep -rin "gcr-secret"
deploy/fake-gpu-operator/templates/device-plugin/_helpers.tpl:63:  - name: gcr-secret
deploy/fake-gpu-operator/templates/gpu-operator/deployment.yml:27:        - name: gcr-secret
deploy/fake-gpu-operator/templates/kwok-gpu-device-plugin/deployment.yaml:39:        - name: gcr-secret
deploy/fake-gpu-operator/templates/mig-faker/daemonset.yml:49:        - name: gcr-secret
deploy/fake-gpu-operator/templates/status-exporter/_helpers.tpl:59:  - name: gcr-secret
deploy/fake-gpu-operator/templates/status-updater/deployment.yaml:41:        - name: gcr-secret
deploy/fake-gpu-operator/templates/topology-server/deployment.yaml:37:        - name: gcr-secret

FYI, when I remove those references, the warning events go away as expected.

If this is by design then we can close this issue.