selftests/tc-testing: add selftests for choke qdisc

Test 8937: Create CHOKE with default setting
Test 48c0: Create CHOKE with min packet setting
Test 38c1: Create CHOKE with max packet setting
Test 234a: Create CHOKE with ecn setting
Test 4380: Create CHOKE with burst setting
Test 48c7: Delete CHOKE with valid handle
Test 4398: Replace CHOKE with min setting
Test 0301: Change CHOKE with limit setting

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