swh-docker-dev and swh-mirror/run-tests both uses Docker containers
bound to port 5080. One to test if the generated images work fine, the
other as part of the mirror stack being tested. To prevent issues,
we explicitly use a volatile resource lock in their pipeline
definitions.
See: https://www.jenkins.io/doc/pipeline/steps/lockable-resources/
We first transform swh-docker-dev from a freestyle job to a Pipeline job in
order to implement fine-grained locked.