Without the CONTEXT variable, the rules for push jobs was broken and
always triggered. This also pulled in the dependency jobs. I don't see a
way to avoid defining the CONTEXT variable in both build and push jobs.

Same as the buster image, but bullseye.

Both latest and buster tags.

- Notify on scheduled pipeline failures.
- Seperate the IMAGE and CONTEXT variables. Allow building where the 2
don't match (planning for httpd/buster and httpd/bullseye).