Tests: Fix integration sudo test
    
    Tests with sudorules using only RunAsGroups attributes with empty RunAsUsers
    attribute fail due to different expected value than is really returned. This is
    caused by improper behaviour of sudo in versions before 1.8.18 (see [1]), to
    which the tests were originally fitted. Changing the expected value to proper
    one.
    
    [1] - https://www.sudo.ws/pipermail/sudo-workers/2016-November/001025.html
    
    https://fedorahosted.org/freeipa/ticket/6378
    
    Reviewed-By: Lukas Slebodnik <lslebodn@redhat.com>