Apply CentOS updates

[arvindshmicrosoft]

• Execute yum update (via. Ansible) to ensure known updates are applied to the OS.
• Thereby, also avoid other high severity security alerts which may be raised when an older, unpatched OS image is used.

[arvindshmicrosoft]

This is probably fine. However, I'd generally expect us to use a more up-to-date image, or rely on some cloud-init stuff which is typically pre-installed on AMIs to do this work, rather than make Ansible responsible for triggering it, which could delay startup significantly. Some updates also require a reboot, so it's not clear that we can even be certain that updates are actually applied as intended this way.

Yeah, you're right. I'll re-think this.

[arvindshmicrosoft]

Closing this as per discussion in #411.