selftests/tc-testing: add selftests for etf qdisc

Test 34ba: Create ETF with default setting
Test 438f: Create ETF with delta nanos setting
Test 9041: Create ETF with deadline_mode setting
Test 9a0c: Create ETF with skip_sock_check setting
Test 2093: Delete ETF with valid handle

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