[1.7.x] Fixed #23754 -- Always allowed reference to the primary key in the admin

This change allows dynamically created inlines "Add related" button to work
correcly as long as their associated foreign key is pointing to the primary
key of the related model.

Thanks to amorce for the report, Julien Phalip for the initial patch,
and Collin Anderson for the review.

Backport of f9c4e14aec from master

tests/admin_views/admin.py

@@ -36,8 +36,8 @@ from .models import (Article, Chapter, Child, Parent, Picture, Widget,
     FilteredManager, EmptyModelHidden, EmptyModelVisible, EmptyModelMixin,
     State, City, Restaurant, Worker, ParentWithDependentChildren,
     DependentChild, StumpJoke, FieldOverridePost, FunkyTag,
-    ReferencedByParent, ChildOfReferer, M2MReference, ReferencedByInline,
-    InlineReference, InlineReferer, Ingredient)
+    ReferencedByParent, ChildOfReferer, ReferencedByInline,
+    InlineReference, InlineReferer, Recipe, Ingredient, NotReferenced)
 
 
 def callable_year(dt_value):
@@ -893,7 +893,6 @@ site.register(Worker, WorkerAdmin)
 site.register(FunkyTag, FunkyTagAdmin)
 site.register(ReferencedByParent)
 site.register(ChildOfReferer)
-site.register(M2MReference)
 site.register(ReferencedByInline)
 site.register(InlineReferer, InlineRefererAdmin)
 
@@ -932,7 +931,9 @@ site.register(EmptyModelHidden, EmptyModelHiddenAdmin)
 site.register(EmptyModelVisible, EmptyModelVisibleAdmin)
 site.register(EmptyModelMixin, EmptyModelMixinAdmin)
 site.register(StumpJoke)
+site.register(Recipe)
 site.register(Ingredient)
+site.register(NotReferenced)
 
 # Register core models we need in our tests
 from django.contrib.auth.models import User, Group