adapt to semanage port dealing with duplicated local customization
    
    The semanage command from older policycoreutils versions (<= 3.6-1.el9)
    behaves in a certain way when a duplicated port context pattern is added.
    It does not add the pattern but produces the following message:
    
      ValueError: Port <protocol>/<number> already defined
    
    The semanage command from new policycoreutils versions (>= 3.6-2.el9)
    behaves differently when a duplicated port context pattern is added.
    It adds the pattern and produces the following message:
    
      Port <protocol>/<number> already defined, modifying instead
    
    Above-mentioned differences in behavior have some consequences for the
    automated test when removing a duplicated port context pattern. If the
    automated test should pass, it needs to anticipate both possibilities.