CUPS uses SIGKILL for Purge-Jobs

[jhamrick]

When the Purge-Jobs command is sent, the jobs are removed, but the current mplayer instance continues playing (this is because a SIGKILL is sent instead of a SIGTERM, so it kills the parent process but not the child process). This unfortunately leads to jobs being played over each other when the CUPS server restarts. We could do something like "make sure there aren't other mplayer process running when a job starts", but that feels hacky. This might be a thing we need to change upstream.

[jhamrick]

We won't need to worry about this anymore once the new IPP server works.