Set the remote writer ref on writer creation

Ensures that status calls to the remote writer correctly
sets the ref.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

services/content/store.go

@@ -115,6 +115,7 @@ func (rs *remoteStore) Writer(ctx context.Context, ref string, size int64, expec
 	}
 
 	return &remoteWriter{
+		ref:    ref,
 		client: wrclient,
 		offset: offset,
 	}, nil