test/IFCFG: make sure the network-legacy plugin is being used
    
    If the network-manager plugin is used instead, it wouldn't write out
    ifcfg files and we wouldn't have anything to check.
    
    While at that, also enable the test.
    
    (cherry picked from commit 2b1b3bcdcb0ddaa18337f18da515adb6284df0ab)
    
    patch_name: 0044.patch
    present_in_specfile: true
    location_in_specfile: 44
    squash_commits: true