fix(capd): remove hack for btrfs/zfs support

Support for btrfs/zfs was upstreamed to kind in kubernetes-sigs/kind#1464, removing the need
for us to hack support in ourselves.

Helps kubernetes-sigs#8317

chore: PR feedback

Removes the now-unused function mountDevMapper(...)

chore: fix ci lint

fix: restore missing storage consts

test/infrastructure/container/docker.go

@@ -52,7 +52,6 @@ const (
 
 	btrfsStorage = "btrfs"
 	zfsStorage   = "zfs"
-	xfsStorage   = "xfs"
 )
 
 type dockerRuntime struct {
@@ -446,15 +445,6 @@ func (d *dockerRuntime) RunContainer(ctx context.Context, runConfig *RunContaine
 	}
 	containerConfig.Env = envVars
 
-	// handle Docker on Btrfs or ZFS
-	// https://github.com/kubernetes-sigs/kind/issues/1416#issuecomment-606514724
-	if d.mountDevMapper(info) {
-		runConfig.Mounts = append(runConfig.Mounts, Mount{
-			Source: "/dev/mapper",
-			Target: "/dev/mapper",
-		})
-	}
-
 	configureVolumes(runConfig, &containerConfig, &hostConfig)
 	configurePortMappings(runConfig.PortMappings, &containerConfig, &hostConfig)