[1.6.x] Fixed #23604 -- Allowed related m2m fields to be references in the admin.

Thanks Simon Charette for review.

Backport of a24cf21722 from master

tests/admin_views/models.py

@@ -716,3 +716,12 @@ class InlineReference(models.Model):
 class InlineReferer(models.Model):
     refs = models.ManyToManyField(InlineReference)
 
+
+# Models for #23604
+class Recipe(models.Model):
+    name = models.CharField(max_length=20)
+
+
+class Ingredient(models.Model):
+    name = models.CharField(max_length=20)
+    recipes = models.ManyToManyField('Recipe', related_name='ingredients')