When `COMMON_ENABLE_DATADOG` is not defined, the datadog-uninstall role runs causing the removal of the apt key and eventually leading to the error below when running `apt-get update`:
```W: Failed to fetch https://apt.datadoghq.com/dists/stable/Release.gpg The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4B4593018387EEAF```
Not sure why a call to uninstall datadog is made by default and think it's best to remove that from running by default. Asked in Slack about it prior to submitting this PR to see if someone with better knowledge of the codebase can justify it, but did not get a response. Guessing it's part of some legacy deployments and is harmless to remove now.
Configuration Pull Request
Make sure that the following steps are done before merging:
[ ] A DevOps team member has approved the PR if it is code shared across multiple services and you don't own all of the services.
[ ] Are you adding any new default values that need to be overridden when this change goes live? If so:
[ ] Update the appropriate internal repo (be sure to update for all our environments)
[ ] If you are updating a secure value rather than an internal one, file a DEVOPS ticket with details.
[ ] Add an entry to the CHANGELOG.
[ ] If you are making a complicated change, have you performed the proper testing specified on the [Ops Ansible Testing Checklist](https://openedx.atlassian.net/wiki/display/EdxOps/Ops+Ansible+Testing+Checklist)? Adding a new variable does not require the full list (although testing on a sandbox is a great idea to ensure it links with your downstream code changes).
[ ] Think about how this change will affect Open edX operators. Have you updated the wiki page for the next Open edX release?