Simplify code related to setting default config values

lib/gitlab/ci/config/entry/policy.rb

@@ -65,7 +65,7 @@ module Gitlab
           end
 
           def value
-            default.to_h.deep_merge(@subject.value.to_h)
+            default.to_h.deep_merge(subject.value.to_h)
           end
         end
       end

lib/gitlab/config/entry/simplifiable.rb

@@ -6,6 +6,8 @@ module Gitlab
       class Simplifiable < SimpleDelegator
         EntryStrategy = Struct.new(:name, :condition)
 
+        attr_reader :subject
+
         def initialize(config, **metadata)
           unless self.class.const_defined?(:UnknownStrategy)
             raise ArgumentError, 'UndefinedStrategy not available!'

spec/lib/gitlab/config/entry/configurable_spec.rb

@@ -30,11 +30,11 @@ describe Gitlab::Config::Entry::Configurable do
   end
 
   describe 'configured entries' do
-    let(:another) { double('another', default: nil) }
+    let(:entry_class) { double('entry_class', default: nil) }
 
     before do
-      entry.class_exec(another) do |another|
-        entry :object, another, description: 'test object'
+      entry.class_exec(entry_class) do |entry_class|
+        entry :object, entry_class, description: 'test object'
       end
     end