Ticket 47411 - Replace substring search with plain search in referint plugin
    
    Bug Description:  RI plugin uses a substring search by default, which is much more
                      expensive than an equality search filter.
    
    Fix Description:  Only use the substring search if the operation is a modrdn.
    
    https://fedorahosted.org/389/ticket/47411
    
    Reveiwed by: richm(Thanks!)
    
    (cherry picked from commit a5dde495a7df7b19fd71cccdb0eb1b91d1f73b58)