Report waived results as pass for TF environment

[mildas]

For TF runs, tmt correctly shows waived results as warn, but then TF shows them as failures and that's a huge mess mainly for our Errata test run where we check for missing identifiers (hundreds of waived rules https://github.com/RHSecurityCompliance/contest/blob/main/conf/waivers/20-long-term#L124).

[comps]

Let's please make a new function, something like on_testingfarm(), right below def have_beaker_api(), that would

return os.environ.get('TESTING_FARM_REQUEST_ID') is not None

and then use that function on the two places.

[mildas]

Closing because of #287