Remove pathMapper object

The use of the pathMapper is no longer needed the way we have organized the
code base. The extra level of indirection has proved unnecessary and confusing
so we've opted to clean it up. In the future, we may require more flexibility,
but now it is simply not required.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

registry/storage/blobwriter.go

@@ -266,7 +266,7 @@ func (bw *blobWriter) validateBlob(ctx context.Context, desc distribution.Descri
 // identified by dgst. The layer should be validated before commencing the
 // move.
 func (bw *blobWriter) moveBlob(ctx context.Context, desc distribution.Descriptor) error {
-	blobPath, err := bw.blobStore.pm.path(blobDataPathSpec{
+	blobPath, err := pathFor(blobDataPathSpec{
 		digest: desc.Digest,
 	})
 
@@ -324,7 +324,7 @@ func (bw *blobWriter) moveBlob(ctx context.Context, desc distribution.Descriptor
 // instance. An error will be returned if the clean up cannot proceed. If the
 // resources are already not present, no error will be returned.
 func (bw *blobWriter) removeResources(ctx context.Context) error {
-	dataPath, err := bw.blobStore.pm.path(uploadDataPathSpec{
+	dataPath, err := pathFor(uploadDataPathSpec{
 		name: bw.blobStore.repository.Name(),
 		id:   bw.id,
 	})