Add 'protected' property setter to LVMVolumeGroupDevice (#1729363)
Add 'protected' property setter to LVMVolumeGroupDevice (#1729363)

Inherited setters do not work after being wrapped using the
SynchronizedMeta meta class.

jkonecny12/blivet,vojtechtrefny/blivet,jkonecny12/blivet,rvykydal/blivet,rvykydal/blivet,vojtechtrefny/blivet