WebUI tests: cover membership management with UI tests
    
    Test cases:
    - admin can add member manager for user/host group
    - admin can add member manager group to user/host group
    - member manager can add user to group
    - member manager can remove user from group
    - member manager can add host to host group
    - member manager can remove host from host group
    
    Ticket: https://pagure.io/freeipa/issue/8298
    
    Signed-off-by: Serhii Tsymbaliuk <stsymbal@redhat.com>
    Reviewed-By: Michal Polovka <mpolovka@redhat.com>