netlabel: Fix a problem when dumping the default IPv6 static labels

There is a missing "!" in a conditional statement which is causing entries to
be skipped when dumping the default IPv6 static label entries.  This can be
demonstrated by running the following:

 # netlabelctl unlbl add default address:::1 \
                                 label:system_u:object_r:unlabeled_t:s0
 # netlabelctl -p unlbl list

... you will notice that the entry for the IPv6 localhost address is not
displayed but does exist (works correctly, causes collisions when attempting
to add duplicate entries, etc.).

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>