Avoid issue usage data

Hi Florian. We had to add another usage event case: the main issue page, which lists all articles and etc. So you can get the changes that I've made to our usage event plugin here:
https://github.com/pkp/ojs/commit/18ceca068c08299bb60878e3c1b40490c4810931

This change required an adaptation to OAS plugin, so it can avoid this new usage event. That's what this pull request is about.