When CentOS detects updates are available, do not FAIL if the updates are unrelated to security

[jgannondo]

Run yum list-security --security or equivalent when script running on CentOS reports that there are updates available to make sure that they are not security updates. Only FAIL when they are security updates and then list which updates were indeed security updates so that the Vendor knows which ones to address.

This is an example of the FAIL state the script will throw when running on CentOS when there are packages that need updating:
[FAIL] There are 25 updates available for this image that have not been installed.

[jgannondo]

Quick clarification:

In the FAIL case (when there are updates available, and some or all of those updates are related to security), the list of updates are security updates should be shown to the user.

[jgannondo]

I'm seeing this issue appear again on an image I'm testing. Here's the relevant output, which shows that the security updates are not being listed. (see [FAIL] line below)

DigitalOcean Marketplace Image Validation Tool v. 1.6
Executed on: Wed Sep 23 18:24:03 UTC 2020
Checking local system for Marketplace compatibility...

Distribution: CentOS Linux
Version: 7

[PASS] Supported Operating System Detected: CentOS Linux
[PASS] Supported Release Detected: 7
[PASS] Cloud-init is installed.
[PASS] Firewall service (firewalld) is active

Checking for available security updates, this may take a minute...

[FAIL] There are 2 security updates available for this image that have not been installed.

Checking for log files in /var/log