Issue 83 - lib389 - Replace topology agmt objects
    
    Bug description: In the lib389 commit that improves
    topology object, we remove "masterX_agmts" key from TopologyMain.
    We use it in our dirsrvtests.
    
    Fix description: Replace the "masterX_agmts" objects with
    inst.agreement functions. We really should stick to one method only.
    
    https://pagure.io/lib389/issue/83
    
    Reviewed by: mreynolds (Thanks!)