This makes the "guess" charm option for storage a littel smarter: instead of using
a blacklist, it avoids any device or partition that is mounted.

This way it will use all available disks, but never "root" (as it will always be mounted),
even if root happens to be on a disk that is not the first one for some reason.
Updated charm helpers.
Added missing network.ip charmhelpers entry.
Added new charmhelpers files.
[tribaal, r=gnuoy] This branch fixes the swift-storage charm's guess config option to ignore disks with mounted partitions instead of using a blacklist.
[gnuoy] Trivial whitespace lint fix