Add method to set the default disklabel (#1078537)
Add method to set the default disklabel (#1078537)

platform.setDefaultDiskLabel(label) will move the disklabel to the front
of the list if it is supported on the current platform and return True.
If it isn't supported it will return False and leave the list as is.

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