New version
    
    - Do not try to get GVariant after not adding anything to its builder (vpodzime)
    - Replace NULL with "" when building ExtraArg (vpodzime)
    - Replace NULL with "" when adding it as a 's' GVariant (vpodzime)
    - Make sure we don't try to add NULL as GVariant to DBus params (vpodzime)
    - Add function for getting recommended thpool metadata size (vpodzime)
    - Make udev settle after we create a LIO device (vpodzime)
    - Always use '--yes' for lvremove (vpodzime)