Support initializing memberof during replication re-init using GSSAPI
    
    The last step of a replication re-initiailization is to run the
    memberof task. The current function would only authenticate using simple
    auth to monitor the task but we may be doing this using admin GSSAPI
    credentials so support that type of bind as well.
    
    In short this fixes:
     # kinit admin
     # ipa-replica-manage re-initialize --from=master.example.com
    
    https://fedorahosted.org/freeipa/ticket/1248