Flags to configure eventing upgrade tests forwarder (ksvc)

[cardil]

This change is required to complete knative/operator#252

It enables configuring of wathola forwarder implemented as Knative Service. Configuration is done by using new optional environment variables.

Proposed Changes

• eventing upgrade tests configuration

[mattmoor]

Produced via:
gofmt -s -w $(find -path './vendor' -prune -o -path './third_party' -prune -o -name '*.pb.go' -prune -o -type f -name '*.go' -print)
goimports -w $(find -name '*.go' | grep -v vendor | grep -v third_party | grep -v .pb.go | grep -v wire_gen.go)

[mattmoor]

Produced via:
prettier --write --prose-wrap=always $(find -name '*.md' | grep -v vendor | grep -v .github | grep -v docs/cmd/)

[mattmoor]

Produced via:
gofmt -s -w $(find -path './vendor' -prune -o -path './third_party' -prune -o -name '*.pb.go' -prune -o -type f -name '*.go' -print)
goimports -w $(find -name '*.go' | grep -v vendor | grep -v third_party | grep -v .pb.go | grep -v wire_gen.go)

[mattmoor]

Produced via:
prettier --write --prose-wrap=always $(find -name '*.md' | grep -v vendor | grep -v .github | grep -v docs/cmd/)

[cardil]

@vaikas does this look good to you now?

[vaikas]

/lgtm
/approve

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cardil, vaikas

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• test/OWNERS [vaikas]

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