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!)