selftests: concurrency: add test to verify parallel add/delete

Implement test that runs 5 instances of tc add filter in parallel with 5
instances of tc del filter from same tp instance. Each instance uses its
own filter handle and key range.

Extend tdc_multibatch.py with additional options required to implement the
test: common prefix for all generated batch files, first value of filter
handle range, MAC address prefix modifier. These are necessary to allow
creating batch files with unique keys and handle ranges with multiple
invocation of tdc_multibatch.py helper script.

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