Fixes #36562 - Clear RootRepo checksum if on_demand repo

[sayan3296]

What are the changes introduced in this pull request?

Upgrade migration to clear checksum_type from RootRepositories for repos with on_demand download policy, before saving the repos.

Considerations taken when implementing this change?

In certain cases where users are upgrading their instance from a very old version of katello (at some point they either have done validate content sync or due to some other really weird reason), They may have a few on_demand repos left with some checksum_type set. But as this combination should not exist and can fail the RemoveDrpmFromIgnorableContent migration, we want to unset the checksum_type for such repos before executing root.save!

What are the testing steps for this pull request?

• Install Katello 4.4
• Enable a few repos ( having on_demand download policy )
• Use a DB query like this to set a specific checksum_type for them i.e.

echo "update katello_root_repositories set checksum_type = 'sha256' where content_type='yum' ;" | su - postgres -c "psql foreman"

• Upgrade to 4.5 and observe the failure during db:migrate
• Apply the changes from this PR
• Re-run db:migrate and it should be successful
• Re-run the upgrade and that should be completed successfully as well.

[theforeman-bot]

Issues: #36562

[chris1984]

ACK works, installer upgraded fine with patch

Upgrade Step 2/2: katello:clean_backend_objects. This may take a long while.
0 orphaned consumer id(s) found in candlepin.
Candlepin orphaned consumers: []
  Success!
  * Foreman is running at https://centos8-stream-katello-4-4.area52.example.com
  * To install an additional Foreman proxy on separate machine continue by running:

      foreman-proxy-certs-generate --foreman-proxy-fqdn "$FOREMAN_PROXY" --certs-tar "/root/$FOREMAN_PROXY-certs.tar"
  * Foreman Proxy is running at https://centos8-stream-katello-4-4.area52.example.com:9090