add grain for detecting mdadm devices
fix jenkins PEP8 & style
Merge branch 'mdadm-grain' of https://github.com/pille/salt into pille-mdadm-grain
Clean up mdadm grain from #16396

Fix open filehandle, and fix traceback on minions with no /proc/mdstat.
Merge branch 'pille-mdadm-grain' into develop