Prioritizing EME test issues

All,

I marked a number of the EME test issues as "VNext", to imply that they are
not essential for this current round of testing. This does not mean we will
not address them, just that they are not essential now.

These issues are listed here:
https://github.com/w3c/web-platform-tests/issues?utf8=%E2%9C%93&q=is%3Aissue%20is%3Aopen%20label%3Aencrypted-media%20milestone%3AVNext%20

Feel free to remove the VNext milestone if you think any of these are
urgent.

...Mark