This doesn't seem inordinately difficult to resolve - lsof can filter on BUILDPLACE, add a flag to kill stray processes, and just kill all the detected processes when that's turned on
This is especially painful with the Jenkins Chroot plugin, which uses
`pbuilder execute` to run things - a stray process from a failed CI test
leads to gigs of "target is busy" messages in the build logs, which need
manually killing.
