/etc/cloud/cloud.cfg
+repo_upgrade: none
-repo_upgrade: security
理由
nginxの1.2.7 => 1.4.3 への変更で下記の仕様が変わり、Etagが削除されてしまっていた
> My problem is that nginx deletes the ETag header from the response even if I
> specify proxy_pass_header ETag.
> The upstream server does return the correct headers:
The ETag header is removed if nginx changes a response returned.
That is, if you have gzip, gunzip, sub, addition, ssi or xslt
filters applied to responses returned.