Improve some error handling in ipa-replica-manage
    
    If you break a replica install after the agreement is created but
    before it gets much further you'll be in the situation where an
    agreement exists, no cn=masters entry exists, and the RUV may not
    be set yet.
    
    This adds some error handling so the broken install can be safely
    removed.
    
    https://fedorahosted.org/freeipa/ticket/3444