Make some PEP8 understandable in run_tests.sh -p

Previously the error message is hard to understand when
some hacking violation such as H803 is detected.
It can be avoided by removing $included_dir from flake8 argument.
As excluded dir is defined in tox.ini, $inlucded_dir is not needed.

Change-Id: I8d1d48fa6feba74ffcec27bf971394b9db727945
Closes-Bug: #1229342
Merge "Make some PEP8 understandable in run_tests.sh -p"