btrfs-progs: use canonical name for device in btrfs fi show when mounted

btrfs-progs: use canonical name for device in btrfs fi show when mounted

When using lvm volumes to check fstests: btrfs/006, it fails like:
     Label: 'TestLabel.006'  uuid: <UUID>
     	Total devices <EXACTNUM> FS bytes used <SIZE>
     	devid <DEVID> size <SIZE> used <SIZE> path SCRATCH_DEV
    +	devid <DEVID> size <SIZE> used <SIZE> path /dev/dm-4
    +	devid <DEVID> size <SIZE> used <SIZE> path /dev/dm-5
    +	devid <DEVID> size <SIZE> used <SIZE> path /dev/dm-6

The /dev/dm-* points to lvm volumes, use @canonicalize_path() to convert them
and we will make it through. Of course we should do the same thing for dev stat.

Signed-off-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>