fix: wait for cloud-init.service to fully activate

[catmsred]

Once the systemd constraint on After cloud-config.service was removed, there are situations where cloud-config.service runs so long after pro that the python code that waits for cloud-config.service to finish activating is being bypassed as if cloud-init isn't on the system. This change forces pro to wait for cloud-config to finish if cloud-init is running at all.

Fixes #3000

Please Squash this PR with this commit message

fix: wait for cloud-init.service to fully activate

Once the systemd constraint on After cloud-config.service was
removed, there are situations where cloud-config.service runs so
long after pro that the python code that waits for
cloud-config.service to finish activating is being bypassed as if
cloud-init isn't on the system.  This change forces pro to wait
for cloud-config to finish if cloud-init is running at all.

Fixes: #3000 
LP: #2059952

Checklist

• I have updated or added any unit tests accordingly
• I have updated or added any integration tests accordingly
• Changes here need to be documented, and this was done in:

Does this PR require extra reviews?

• Yes
• No

[github-actions]

Jira: This PR is not related to a Jira item. (The PR title does not include a SC-#### reference)

GitHub Issues: No GitHub issues are fixed by this PR. (No commits have Fixes: #### references)

Launchpad Bugs: No Launchpad bugs are fixed by this PR. (No commits have LP: #### references)

Documentation: The changes in this PR do not require documentation changes.

👍 this comment to confirm that this is correct.

[catmsred]

Verified that it fixed the issue in GCP using a custom image with this branch's pro on it:

$ gcloud compute instances create pro-order-bug-custompro --image testing-ubuntu-pro-2204-jammy-v20240328 --image-project ubuntu-catred --metadata-from-file=user-data=userdata.yaml

catred@pro-order-bug-custompro:~$ pro status
SERVICE          ENTITLED  STATUS       DESCRIPTION
anbox-cloud      yes       disabled     Scalable Android in the cloud
esm-apps         yes       disabled     Expanded Security Maintenance for Applications
esm-infra        yes       disabled     Expanded Security Maintenance for Infrastructure
fips-preview     yes       disabled     Preview of FIPS crypto packages undergoing certification with NIST
usg              yes       disabled     Security compliance and audit tools

For a list of all Ubuntu Pro services, run 'pro status --all'
Enable services with: pro enable <service>

                Account: ubuntu-catred
           Subscription: ubuntu-catred
            Valid until: Fri Dec 31 00:00:00 9999 UTC
Technical support level: essential
catred@pro-order-bug-custompro:~$ cat /var/log/cloud-init.log | grep 'WARNING'
catred@pro-order-bug-custompro:~$ 

[renanrodrigo]

Thanks for this one!
LGTM