Revert "Merge pull request rails#27098 from sina-s/fix-unexpected-session-sharing"

This reverts commit cbf2e7a.

While this bug is a legitimate bug, this method has been broken in this
exact way for quite some time. Any code that is using this method is
almost certainly doing it wrong, as it's pretty much impossible to use
correctly. That code will all be broken by this change.

While this is a good bug fix, and should happen for 5.1, and this method
is only used for tests, we should not break all of the code using it in
a point release.

Author: sgrif

actionpack/lib/action_dispatch/testing/integration.rb

@@ -453,7 +453,6 @@ def remove! # :nodoc:
       # simultaneously.
       def open_session
         dup.tap do |session|
-          session.reset!
           yield session if block_given?
         end
       end

actionpack/test/controller/integration_test.rb

@@ -583,14 +583,6 @@ def test_request_with_bad_format
     end
   end
 
-  test "creation of multiple integration sessions" do
-    integration_session # initialize first session
-    a = open_session
-    b = open_session
-
-    refute_same(a.integration_session, b.integration_session)
-  end
-
   def test_get_with_query_string
     with_test_route_set do
       get '/get_with_params?foo=bar'

railties/CHANGELOG.md

@@ -1,11 +1,5 @@
 ## Rails 5.0.1.rc1 (December 01, 2016) ##
 
-*   Reset a new session directly after its creation in ActionDispatch::IntegrationTest#open_session
-
-    Fixes Issue #22742
-
-    *Tawan Sierek*
-
 *   Add `:skip_sprockets` to `Rails::PluginBuilder::PASSTHROUGH_OPTIONS`
 
     *Tsukuru Tanimichi*