Issue 7 - Add pause and resume methods to topology fixtures
    
    Description: For testing purposes, sometimes we need to pause the
    replication on a big amount of agreements (4 and more, for instance).
    Add the methods to the TopologyMain class of lib389/topologies.py module.
    
    https://pagure.io/lib389/issue/7
    
    Reviewed by: wibrown (Thanks!)