updated the quickstart to work on OpenShift v2 cartridges

Hi!

I made some small changes to the Sentry quickstart so it can run on new v2 cartridges on OpenShift. Some of the paths and env variables were changed as can be seen [here](https://www.openshift.com/blogs/important-changes-in-the-new-version-2-cartridge-format) and [here](https://www.openshift.com/blogs/version-2-cartridge-update-action-may-be-required).