tests: add F28 CI tests using the Standard Test Interface
    
    Adding initial set of basic functionality tests for NetworkManager
    according to the Standard Test Interface [1]. See Quick Start Guide
    for brief introduction about how to run these tests [2].
    
    [1] https://fedoraproject.org/wiki/CI/Standard_Test_Interface
    [2] https://fedoraproject.org/wiki/CI/Quick_Start_Guide
    
    [thaller@redhat.com: at this point, NetworkManager package on rawhide
      is essentially the same as on f28. So, when cherry-picking the
      tests, also intentionally keep testing the "fedora28" profile.
       1) until the packages that we test diverge, there is usually
          little reason to run a different set of tests (unless it
          makes sense due to differences in the Fedora version).
       2) as long as the set of tests that we want to run is identical,
          there is no reason to clone the test profile and bump the
          profile number.
      It follows: we stick to "fedora28" for the time being.]
    
    (cherry picked from commit c8e00774af63d2e13282df5d278cf409fc2717ae)