resolve: fix misuse of accuracy parameter in sd_event_add_time()
    
    Also, this makes mDNS regular queries sent without delay (except for
    one caused by the default accuracy of sd-event).
    
    Note, RFC 6762 Section 5.2 is about continuous mDNS query, which is not
    implemented yet.
    
    (cherry picked from commit 765647ba805727e93ac8607e38c7b60da2aab2dd)