[base] Do not generate locale configuration, under `Circle CI` container.

```
diff --git a/site-cookbooks/base/recipes/default.rb b/site-cookbooks/base/recipes/default.rb
index 21c333e..40e9c11 100644
--- a/site-cookbooks/base/recipes/default.rb
+++ b/site-cookbooks/base/recipes/default.rb
@@ -51,9 +51,14 @@ script "Language Settings" do
   group "root"

   code <<-EOH
-  locale-gen ja_JP.UTF-8
-  dpkg-reconfigure locales
-  update-locale LANG=ja_JP.UTF-8
+  # Under the Circle CI environment,
+  # do not generate locale.
+
+  if [ -z ${CIRCLECI} ]; then
+    locale-gen ja_JP.UTF-8
+    dpkg-reconfigure locales
+    update-locale LANG=ja_JP.UTF-8
+  fi
   EOH
 end
```