Ticket 49890 : ldapsearch with server side sort crashes the
     ldap server
    
    Bug Description:
            Server side sort with a specified matching rule trigger a crash
    
    Fix Description:
            Check if the we are able to index the provided value.
            If we are not then slapd_qsort returns an error (LDAP_OPERATION_ERROR)
    
    https://pagure.io/389-ds-base/issue/49890
    
    Reviewed by: mreynolds
    
    Platforms tested: F27
    
    Flag Day: no
    
    Doc impact: no
    
    (cherry picked from commit c989e18f7a3da060b16d39919b920b6b2a19a0ac)