`knative-eventing-injection` can't be used with private registry

[duglin]

Describe the bug
While trying to get the e2e tests to work using a private registry, I found that the tests that add the knative-eventing-injection label to a namespace will fail because the pods that get automatically created will fail to be able to pull the needed images. This is because those pods are associated with the eventing-broker-filter ServiceAccount which was also automatically created and there doesn't appear to be a way to inject a pull secret into that service account.

To Reproduce
Run the e2e tests with all images in a private registry.

Knative release version
v0.8.0

/cc @n3wscott

[duglin]

To be clear, I think this is an issue with Eventing itself, not the test infrastructure since this situation will happen during normal usage not just testing.

[grantr]

Good catch. This does seem to be a fundamental issue with the approach, and should at least be documented.

[akashrv]

/assign @duglin

[akashrv]

/milestone v0.10.0

[lionelvillard]

/assign

[lionelvillard]

/unassign
/assign @beemarie