BE: search with sysdb_search_with_ts_attr
    
    Previously, the background refresh code had used sysdb_search_entry()
    which does not run the search on the timestamp cache. Instead, this
    patch changes to using sysdb_search_with_ts_attr with the
    SYSDB_SEARCH_WITH_TS_ONLY_TS_FILTER optimization because currently only
    the dataExpireTimestamp attribute is included in the filter.
    
    Related:
    https://pagure.io/SSSD/sssd/issue/4012
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>