Ticket 48360 - Refactor the delete agreement function
    
    Description: The delete agreement function of agreement.py module
    doesn't cover all usage varieties and should be rewritten.
    
    Now it requires suffix and replica(DirSrv object of the server
    that the agreement points to). By some reasons, this replica object
    may be missing, then we couldn't delete the agreement.
    
    We don't have test coverage for that function.
    It should be added to tests/agreement_test.py.
    
    Also test_changes fails, fix is required.
    
    Fix description: Change arguments of the delete agreement function to:
    - suffix
    - consumer_host - of the server that the agreement points to
    - consumer_port - of the server that the agreement points to
    or
    - agmtdn - DN of the replica agreement
    
    With that, we can clearly define the required agreement.
    
    Add the delete test to tests/agreement_test.py
    
    Also fix the changes test by adding time.sleep(2) before
    change number checking, because there was not enough time
    for updating change number on master.
    
    https://fedorahosted.org/389/ticket/48360
    
    Reviewed by: wibrown (Thanks!)