Use a volatile resource lock for host port 5080

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/