Fall back to parted to detect dasd disklabels.

blkid does not know how to detect dasd disklabels, so we cannot rely on
the information provided by udev in this case.

Resolves: rhbz#1144410
Raise an exception when we find orphan partitions.

If we find a partition that belongs on a disk that we did not find a
disklabel on (or a hidden format or an iso9660 fs) we have serious
enough problems to justify raising an exception instead of quietly
ignoring it. Ignoring these partitions almost always ends up causing
fatal problems further along.

Related: rhbz#1144410
Return early when setting new size for non-existent partition.

Related: rhbz#978266
Fix some pylint errors introduced in recent commits.