device_cmp() evaluates the result, nat->masq_index
may already have been changed (regardless if the lock is there or not).

So, the lock either has to be held during nf_ct_iterate_cleanup(),
or can be removed.

This does the latter.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
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