Reflect ability to register or join waitlist on the register button

This needs review.

I just tested the patch from the MR and it doesn't seem to be working accordingly.

Module version: 2.0.1

1. Create a new event series
2. Set to happen every monday
3. Set capacity: 3
4. Enable registration
5. Enable waitlist
6. Save the event series
7. Access the events list

Result: Join Waitlist button is displayed when there are no registrants.

Here's a screencast of the steps above. →

That is so odd, I followed those same steps and watched your video, but it works for me. Hmm. I'll need to debug some to try and recreate it locally.