Add locales and make sure to upgrade packages (#1218)
Add locales and make sure to upgrade packages (#1218)

This PR:
- Add the locales-all package so that `yamllint` can proper parse UTF-8 symbols
- Upgrade `yamllint` package to latest; it has locale-related improvements
- Run `apt-get dist-upgrade` to make sure packages are always updated when building the image
istio/tools,istio/tools,istio/tools,istio/tools,istio/tools,istio/tools