genetlink: prevent memory leak in netlbl_unlabel_defconf

[David Miller]

From: Paul Moore <paul at paul-moore.com>
Date: Fri, 27 Sep 2019 10:48:54 -0400

> From what I've seen the "Fixes" tag is typically used by people who
> are backporting patches, e.g. the -stable folks, to help decide what
> they need to backport.

Fixes: tags say what commit introduced the code being fixed, whether
it manifests in a real problem or not.

It has nothing directly to do with -stable and exists in it's own right
whether a change gets backported to -stable or not.