`get_token/1,2,3` claim to return `max_tokens` when the limit is reached but in fact they return `max_concurrency`:

```
3> riak_core_bg_manager:set_token_rate(a, {10000, 2}).
0
4> riak_core_bg_manager:get_token(a).
ok
5> riak_core_bg_manager:get_token(a).
ok
6> riak_core_bg_manager:get_token(a).
max_concurrency
```