Do supercall in BTRFSVolumeDevice.formatImmutable.
Do supercall in BTRFSVolumeDevice.formatImmutable.

That way we can take into account if the device is protected, even if it
is non-existant.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

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