tc-testing: add selftests for 'bpf' action

tc-testing: add selftests for 'bpf' action

Test d959: Add cBPF action with valid bytecode
Test f84a: Add cBPF action with invalid bytecode
Test e939: Add eBPF action with valid object-file
Test 282d: Add eBPF action with invalid object-file
Test d819: Replace cBPF bytecode and action control
Test 6ae3: Delete cBPF action
Test 3e0d: List cBPF actions
Test 55ce: Flush BPF actions
Test ccc3: Add cBPF action with duplicate index
Test 89c7: Add cBPF action with invalid index
Test 7ab9: Add cBPF action with cookie

Changes since v1:
 - use index=2^32-1 in test ccc3, add tests 7a89, 89c7 (thanks Roman Mashak)
 - added test 282d

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>