test/cache::catchup_all: fix unread items counting
test/cache::catchup_all: fix unread items counting

The gist of the bug this fixes is:

-if (! item->unread()) {
+if (item->unread()) {

In other words, we treated unread items as read when counting.

The rest of the changes just restore the test to the form it should've
been in from the very beginning.

x4121/newsbeuter,newsboat/newsboat,der-lyse/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,der-lyse/newsboat,newsboat/newsboat,der-lyse/newsboat,newsboat/newsboat,x4121/newsbeuter,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,x4121/newsbeuter,der-lyse/newsboat,newsboat/newsboat,x4121/newsbeuter,newsboat/newsboat