Adapt multipath detection code to external pyudev module.
Adapt multipath detection code to external pyudev module.

The main difference is that we can't write to pyudev.Device instances.

rvykydal/blivet,rvykydal/blivet,vojtechtrefny/blivet,vojtechtrefny/blivet,dwlehman/blivet,jkonecny12/blivet,jkonecny12/blivet,AdamWill/blivet,rhinstaller/blivet,dwlehman/blivet,AdamWill/blivet,vpodzime/blivet,vpodzime/blivet,rhinstaller/blivet