Add database pod and service for ruby sample app demo

- [x] update ruby-sample-app image with MySQL connection for Sinatra app 
- [x] change docker image URL with OpenShift official image for ruby-sample-app - https://github.com/openshift/ruby-hello-world/pull/5
This might be a good case to use the value generator instead, where we explicitly state the value, and pick a nice DB name, instead of generating a random one.