selftests/tc-testing: add selftests for codel qdisc

Test 983a: Create CODEL with default setting
Test 38aa: Create CODEL with limit packet setting
Test 9178: Create CODEL with target setting
Test 78d1: Create CODEL with interval setting
Test 238a: Create CODEL with ecn setting
Test 939c: Create CODEL with ce_threshold setting
Test 8380: Delete CODEL with valid handle
Test 289c: Replace CODEL with limit setting
Test 0648: Change CODEL with limit setting

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>