Add virt-who plugin tests to Satellite Jenkins CI

[hkx303]

Description
Now, we are using the new structure for virt-who plugin testing. To test virt-who cases, we should only have robottelo.properties and virtwho.properties and then, run the Pytest command(pytest robottelo/tests/foreman/virtwho). it is easier to consolidate the virt-who plugin test cases to Jenkins jobs.
We would like to make it a stage in the satellite pipelines recently. And it is also our goal, as peer https://docs.engineering.redhat.com/display/SQE/Plugin+Integration+Testing

Info for virt-who tests:

1. About 78 test cases
2. Tests need about 6 hours