Fix monkey patching in Django 1.7 and newer

django.db.backends.util was deprecated and replaced with django.db.backends.utils in Django 1.7.
Here we import util in Django 1.6 and older, and utils otherwise.
Instead of checking the version, what about:

```python
try:
    from django.db.backends import utils as util
except ImportError:
    from django.db.backends import util
```