KAZOO-3217: conferences: play name on join feature

Why not just call into `while/4`?

```erlang
while(Predicate, LoopBody) ->
    while(Predicate, LoopBody, 'ok', 'true').
```

Should start the recursion and minimize duplicated code executing `LoopBody`. Also, why not name it `GeneratorFun` or similar; that's really what the variable repreresents.