selftests: forwarding: tc_common: Add hitting check

Add an option to check that packets hit the tc filter without providing
the exact number of packets that should hit it.

It is useful while sending many packets in background and checking that
at least one of them hit the tc filter.

Signed-off-by: Amit Cohen <amitc@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>