Delete python bytecode before every test run

Bring over the cleaning line from run_tests.sh for the pyc files to
all the tox runs.

This should eliminate the need to clean -x -i to kill pyc files in
your local directory to get tests to pass.

Change-Id: Id236061c60ed5558459ef67752e0f504c5818b5c
Closes-Bug: #1368661

tox.ini

@@ -12,7 +12,10 @@ setenv =
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 whitelist_externals = bash
-commands = nosetests -w tests/ -e tests_to_fix
+                      find
+commands =
+  find . -type f -name "*.pyc" -delete
+  nosetests -w tests/ -e tests_to_fix
 
 [testenv:pep8]
 commands = flake8