SDAP: Immediately finish request for empty array
    
    If array of sids is empty we needn't try to resolve them
    and we can immediately finish request in function sdap_ad_resolve_sids_send
    This patch is just a small optimisation.
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    (cherry picked from commit 21f2821a4420291c8eb3ee9d427e9e1b0a1d9989)