See
https://bugzilla.redhat.com/show_bug.cgi?id=1212841
Currently is not possible to add new partitions to disk with an existing LVM VG.
'findActiveDevicesOnActionDisks' should disallow only actions involving changes on
the disklabel not adding new partitions.
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To view this pull request on github, visit
https://github.com/rhinstaller/blivet/pull/93