Ensure that LANG is set for all Ruby containers

As seen in the 2018-04-13 demo, we're running into issues with UTF-8 encoding issues from PostgreSQL after using the Web IDE/UI to change a file. It appears that the Ruby/Rails containers are note recognizing that they should be using UTF-8, despite a number of attempts to enforce it (as seen in gitlab-org/build/CNG!63 (merged))

I'm suggesting that we explicitly set the LANG/LC_ALL environment variable to C.UTF-8 for unicorn and sidekiq charts, so that we know they are enforced at deployment.