Ticket 47590: CI tests: add/split functions around replication
    
    Bug Description:
    	Functions to setup replication are a bit too complex. They do a lot of things that
    	should be split in several simpler functions.
    	The parameters are also complex with mandatory/optional.
    
    Fix Description:
    	The fix implements:
    		- delSchema(attr, val)
    		- getSchemaCSN(instance)
    		- New class Agreement (in brooker)
    			- status
    			- schedule
    			- create
    			- init
    			- checkProperties
    			- _check_interval
    		- reorganise routine from lib389 and brooker.replica to brooker.Agreement
    		  (init, status, create, schedule)
    		- Creation of a default replica Mgr moved from lib389
    		  to brooker.replica.create_repl_manager
    		- Add a fix into instancebackupFS to backup changelog directory
    
    https://fedorahosted.org/389/ticket/47590
    
    Reviewed by: Roberto Polli, Rich Megginson (Many thanks for all your Help Roberto and Rich)
    
    Flag Day: no
    
    Doc impact: no