Revert "Merge pull request #7983 from georgebrock/bug7950-squashed"

This reverts commit 88a296dccc, reversing
changes made to 666a7e34f5.

Conflicts:
	activerecord/CHANGELOG.md

Reason: this has been resulting in some hard to track bugs and is
introducing a possible breackage in a stable version.

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -1225,13 +1225,6 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert companies(:first_firm).clients.include?(Client.find(2))
   end
 
-  def test_included_in_collection_for_new_records
-    client = Client.create(:name => 'Persisted')
-    assert_nil client.client_of
-    assert !Firm.new.clients_of_firm.include?(client),
-           'includes a client that does not belong to any firm'
-  end
-
   def test_adding_array_and_collection
     assert_nothing_raised { Firm.find(:first).clients + Firm.find(:all).last.clients }
   end