Array.reindex silently ignores new_axis argument when first argument is an Axis

While looking at the code of reindex for #1120 , I noticed the following bug:

```python
>>> arr = ndtest(3)
>>> arr.reindex("a", "a1,a2,a3")
a   a1   a2   a3
   1.0  2.0  nan
>>> arr.reindex(arr.a, "a1,a2,a3")
a   a0   a1   a2
   0.0  1.0  2.0
```

Very high priority because this is a silent failure. I think fixing this should only be a matter of adding "and new_axis is None".