Add docs about needed cluster roles for e2e operator tests

[jberkhahn]

Description of the change:
Add docs about the needed permissions for running e2e operator tests.

Motivation for the change:
As discussed in #1082 this is useful information for users in environments where they might not be running as cluster-admin by default.

Closes #1082

[jberkhahn]

are changes to /website supposed to be done manually? I submitted a previous docs PR that didn't fail the travis build.

[camilamacedo86]

I am ok with the content. Really thank you for your collab. 👍
Also, now we need to copy the same charges to .website/ dir. (it is temporary only, sorry for the inconvenience)
Could you please do that?

[camilamacedo86]

Hi @jberkhahn,

The docs in a transition period. Temporary, we need to copy to keep both equals. So, yes. For we are able to move forward and it passes in the CI you need to perform the same changes in website/content/en/docs/test-framework/writing-e2e-tests.md. Could you please do that?

[jberkhahn]

/retest

[openshift-ci-robot]

@jberkhahn: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

Details

In response to this:

/retest

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[jberkhahn]

this should be good to go?

[estroz]

/lgtm