qa: add api test for nfct_cmp and nfct_exp functions

Some of these checks will fail due to errors in nfct_cmp STRICT handling
and missing comparision of attributes in the nfexpect_cmp functions.

Signed-off-by: Florian Westphal <fw@strlen.de>
conntrack, expect: fix _cmp api with STRICT checking

Normal comparision succeeds when the _common_ attribute subset
have same values.

When STRICT matching is specified, the comparision should succeed only when
both objects have same attribute subset and attribute values match.

However, STRICT comparision often fails as an attribute missing in both
objects is erronously considered an error.

Signed-off-by: Florian Westphal <fw@strlen.de>
expect: consider all expect attributes when comparing

The expect cmp function ignored most of the attributes.

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