Ticket 48322 - Allow reindex function to reindex all attributes
    
    Bug Description:  Currently the task reindex function requires an attribute
                      name.  This does now allow the task to reindex all of a
                      backend's indexes(like db2index.pl can do)
    
    Fix Description:  If the attrname is not provided, search for all the backend's
                      attribute indexes, and reindex them.
    
    https://fedorahosted.org/389/ticket/48322
    
    Reviewed by: spichugi(Thanks!)