fixes bug 1064608 - CurrentProducts gets called too often

@rhelmer r?

This reduces it in half just in the tests. 

What those 4 lines do is effectively what `models.CurrentVersions.get` does. Actually, it's exactly the same but done with a for loop instead. 

Nested list comprehensions are neat but they hurt the brain so much that I hate them. It's been less than 24 hours and I have not forgotten how this one works. 

I filed a bug to deprecate `models.CurrentVersions` and `models.ProductsVersions` since they are little wrappers instead of actual layers on top of the middleware. I still like the functionality (e.g. getting a flat list of ALL versions across all products) so what I might do is copy this list comprehension code above into a method or static method on the `models.CurrentProducts` class. E.g. Instead of...:
```python
versions = models.CurrentVersions().get()
```
we'd do...:
```python
```