filter_event_permalink filters any call to get_permalink while event is the global post

[filter_event_permalink](https://github.com/Automattic/eventbrite-api/blob/master/inc/class-eventbrite-query.php#L384) will filter **all** calls to `get_permalink` while the global $post is the event.

Eg. I was iterating over a list of plain, non-event post objects within the `eventbrite-single.php` intending to output their permalinks, but calls such as `get_permalink($my_post)` will always return the permalink for the current event.

I tried to add $post as an arg to `filter_event_permalink` so it would only conditionally change the permalink but the arg never seemed to be populated.

My work around was to just call `setup_postdata($my_post)` and `wp_reset_postdata()` for every post object. Hope it saves someone some time.