selftests: concurrency: add test to verify concurrent replace

Implement test that verifies concurrent replacement of rules by executing
10 tc instances that replace flower filters in same handle range.

Extend tdc_multibatch.py script with new optional CLI argument that is used
to generate all batch files with same filter handle range.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>