Model field default callable called twice in forms

[Nitesh Lohchab]

callable assigned to default parameter of a field called twice when adding a model entry via admin.

behaviour to reproduce this:

---

def abc():
    print "this is abc"
    return "abc"


class testt(models.Model):
    text = models.CharField(max_length=12, default=abc)

---

Now when you try to add this model via admin you will see "this is abc" printed twice in console.

[Tim Graham]

Likely a duplicate of #11390.