cephfs: use os.Remove to remove directory

using os.RemoveAll will remove everything
in the director after the Umount we should
be using os.Remove only to remove the empty
directory

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/cephfs/nodeserver.go

@@ -636,7 +636,7 @@ func (ns *NodeServer) NodeUnpublishVolume(
 		isMnt = true
 	}
 	if !isMnt {
-		if err = os.RemoveAll(targetPath); err != nil {
+		if err = os.Remove(targetPath); err != nil {
 			return nil, status.Error(codes.Internal, err.Error())
 		}