Revert params.fetch to params.expect conversions in scaffold

The conversions have the unintended consequence of requiring params
when none are expected. Ensure generated templates work as is.
Adds a missing test for the api controller generation.

Originally pointed out in rails/jbuilder#573.

railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb.tt

@@ -48,7 +48,7 @@ class <%= controller_class_name %>Controller < ApplicationController
     # Only allow a list of trusted parameters through.
     def <%= "#{singular_table_name}_params" %>
       <%- if attributes_names.empty? -%>
-      params.expect(<%= singular_table_name %>: {})
+      params.fetch(:<%= singular_table_name %>, {})
       <%- else -%>
       params.expect(<%= singular_table_name %>: [ <%= permitted_params %> ])
       <%- end -%>

railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb.tt

@@ -55,7 +55,7 @@ class <%= controller_class_name %>Controller < ApplicationController
     # Only allow a list of trusted parameters through.
     def <%= "#{singular_table_name}_params" %>
       <%- if attributes_names.empty? -%>
-      params.expect(<%= singular_table_name %>: {})
+      params.fetch(:<%= singular_table_name %>, {})
       <%- else -%>
       params.expect(<%= singular_table_name %>: [ <%= permitted_params %> ])
       <%- end -%>

railties/test/generators/scaffold_controller_generator_test.rb

@@ -67,7 +67,7 @@ def test_dont_use_require_or_permit_if_there_are_no_attributes
 
     assert_file "app/controllers/users_controller.rb" do |content|
       assert_match(/def user_params/, content)
-      assert_match(/params\.expect\(user: \{\}\)/, content)
+      assert_match(/params\.fetch\(:user, \{\}\)/, content)
     end
   end
 
@@ -357,6 +357,15 @@ def test_api_only_generates_params_for_attachments
     end
   end
 
+  def test_api_only_doesnt_use_require_or_permit_if_there_are_no_attributes
+    run_generator ["User", "--api"]
+
+    assert_file "app/controllers/users_controller.rb" do |content|
+      assert_match(/def user_params/, content)
+      assert_match(/params\.fetch\(:user, \{\}\)/, content)
+    end
+  end
+
   def test_check_class_collision
     Object.const_set :UsersController, Class.new
     content = capture(:stderr) { run_generator }