Bug 661102 - Rename of managed entries not handled correctly
    
    When usign the managed entry plug-in, a modify operation against
    an origin entry that should trigger a rename of a managed entry
    does not trigger the rename.  In addition, an error message is
    logged since we try to do a modify of the RDN attribute of the
    managed entry.
    
    This patch makes the modify callback check if the changes require
    a rename of the managed entry when an origin entry is updated.  If
    a rename is needed, we perform a MODRDN.  We also need to skip the
    RDN attribute when generating the mapped modifications that we use
    to update a managed entry.