Bug 671033 - range sharing between server breaks with SASL/GSSAPI auth
    
    The DNA range request extop uses the replication bind credentials
    to authenticate to the other master.  If the replication agreement
    is configured to use SASL/GSSAPI (or any non simple bind auth), the
    DNA plug-in falls back to using an anonymous bind, which will fail.
    
    The problem is that the function that fetches the replication bind
    credentials was expecting a bind dn and password.  If both of these
    were not found, it would free everything (including the bind
    method).  The fix is to just fetch the credentials and return them
    without doing this additional check.
    
    This patch also makes the receiving master check if the bind DN
    matches any replication bind DN, which allows it to work properly
    when multiple replication bind DNs are configured.  It previously
    only worked with a single-valued replication bind DN attribute.