[actions] Trigger publish-build-containers workflow on PR without pushing
[actions] Trigger publish-build-containers workflow on PR without pushing

When a PR is made against the dockerfiles in `docker/build` we should trigger
the workflow to make sure this is building fine on all container flavors, just
not push the image.

iovisor/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc