waitlist: fix userInWaitlist check, fixes #70
waitlist: fix userInWaitlist check, fixes #70

Fixes a similar issue as 3ab25ff.

Also checks the current DJ, so that the Join Waitlist button does
not appear when you're DJing.

welovekpop/uwave-web-welovekpop.club,u-wave/web,welovekpop/uwave-web-welovekpop.club,u-wave/web