conntrack: nfct_cmp: also compare labels

Signed-off-by: Florian Westphal <fw@strlen.de>
qa: nfct_cmp: verify individual attr comparision

For each attribute:
 - copy ct2 attrs to ct1 (so they're the same)
 - change value of attr
 - call nfct_cmp to check of cmp now fails

Unfortunately, most attributes fail this test at this time, thus
added a TODO exclusion list to make the test pass for now.

Signed-off-by: Florian Westphal <fw@strlen.de>
connlabel: fix NULL deref on malloc failure

Signed-off-by: Florian Westphal <fw@strlen.de>