No functional changes. Fixes for things that PyLint complains about, but
are safe to change anyway, as well as a minor improvement to a docstring
that referenced non-existant args.
This touches files that are mpm.conf-related.
- Allow to set default args via config file
- Read them from prefs API
- override-db-pids uses the same APIs now ([overrides] section in
config file, prefs API, and same dictionary as --default-args when
used on the command line
