Reset the logs in packagers_without_bugzilla for every message
    
    Otherwise we keep in memory the logs from the previous runs which
    renders the email sent to the admins a little hard to read.
    
    For example on day one, you have user1 and user2 without a bugzilla
    account (then logs contain user1 and user2). Then on day two, user1 and
    user3 are also without a valid bugzilla account (logs = user1, user2,
    user1, user3) then on day three only user3 is left (logs = user1, user2,
    user1, user3, user3) and so on...
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>