notmuch: use exclude tags for entrie-thread too

Signed-off-by: Karel Zak <kzak@redhat.com>
notmuch: call notmuch_query_count_messages() more carefully

 - it seems that notmuch is sensitive when notmuch_query_count_messages()
   is called, let's call it when we really need the number for progress bar

 - initialize mutt progress bar when we really want to use it

References: https://github.com/karelzak/mutt-kz/issues/57
Signed-off-by: Karel Zak <kzak@redhat.com>