Allow disabling of E2E test metrics gathering

[jgwest]

What does this PR do / why we need it:

• Currently, when the Rollout E2E tests are run against operator that has been installed via OLM (using Subscription), or generally if the operator controller is running on the cluster rather than locally, then metrics gathering will fail.
• This PR thus adds a parameter which can be set to disable metrics gathering in unsupported configurations (OLM-installed Subscriptions)

[Rizwana777]

/lgtm

[jgwest]

Thanks @Rizwana777!