tc: python3, string formattings

This patch converts old type string formattings to new type string
formattings for adapting Linux Traffic Control (tc) unit testing suite
python3.

Linux Traffic Control (tc) unit testing suite's code quality improved is improved with this patch.
According to python documentation;
"The built-in string class provides the ability to do complex variable substitutions and
value formatting via the format() method described in PEP 3101. "
but the project was using old type formattings and new type string formattings together,
this patch's main purpose is converting all old types to new types.

Following files changed:
 1. tools/testing/selftests/tc-testing/tdc.py
 2. tools/testing/selftests/tc-testing/tdc_batch.py

Following PEP rules applied:
 1. PEP8 - Code Styling
 2. PEP3101 - Advanced Code Formatting

Signed-off-by: Batuhan Osman Taskaya <batuhanosmantaskaya@gmail.com>

Signed-off-by: David S. Miller <davem@davemloft.net>