[ART-672] Declare manifests on sriov-network-operator

[thiagoalessio]

Attempt to address failed build:

{"x86_64": {"export_operator_manifests": "RuntimeError(
    'Could not extract operator manifest files.
    Is there a /manifests path in the image?
    404 Client Error: Not Found ({"message":
    "lstat /var/lib/docker/overlay2/.../merged/manifests: no such file or directory"

https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=22224111

[adammhaile]

The owner needs to either create a release-4.2 branch or make master correct.
art is not a valid branch name in this case.

[thiagoalessio]

got it @adammhaile , thanks! closing this PR in favor of openshift/sriov-network-operator#2