function cleanArrReferences(arr) {
      for (var i = 0; i < arr.length; i++) {
        delete arr[i].fn;
      }
    }
Cleans up the references to all the deferred functions
(before/after/beforeEach/afterEach) and tests of a Suite.
These must be deleted otherwise a memory leak can happen,
as those functions may reference variables from closures,
thus those variables can never be garbage collected as long
as the deferred functions exist.

@private