[1.7.x] Fixed #22823 (and partly #22563) - FKs from unmigrated apps breaking state.

Thanks to bendavis78 for the test and diagnostic work.

tests/migrations/migrations_test_apps/unmigrated_app/models.py

@@ -0,0 +1,9 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+from django.db import models
+
+
+class SillyModel(models.Model):
+    silly_field = models.BooleanField(default=False)
+    silly_tribble = models.ForeignKey("migrations.Tribble")
+    is_trouble = models.BooleanField(default=True)