Evaluation in debugger must be done within the namespace of instrumented form

Do in a tmp.clj (user namespace)

```clj
(defn foo [a]
  (bar a))

(defn bar [b]
  (+ 1 b))
```

Then from another namespace do `(foo 1)` once you are after `(bar a)` eval with `C-x C-e`. you should get `   Unable to resolve symbol: bar in this context`.  

It's probably easy to fix. Will have a look once clojure-emacs/cider-nrepl#405 is merged. 