Check for the existence of a replication agreement before deleting it.
    
    When using ipa-replica-manage or ipa-csreplica-manage to delete an
    agreement with a host we would try to make a connection to that host
    prior to tryign to delete it. This meant that the trying to delete
    a host we don't have an agreement with would return a connection
    error instead of a "no agreement with host foo" error.
    
    Also display a completed message when an agreement is removed.
    
    https://fedorahosted.org/freeipa/ticket/2048
    https://fedorahosted.org/freeipa/ticket/2125