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: Ibcc824370ed3d48835780cca6c1075856f1dfacc
Closes-Bug: #1368661

tox.ini

@@ -16,7 +16,10 @@ setenv = VIRTUAL_ENV={envdir}
          NOSE_OPENSTACK_STDOUT=1
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = nosetests {posargs}
+commands = find . -type f -name "*.pyc" -delete
+           nosetests {posargs}
+
+whitelist_externals = find
 
 [tox:jenkins]
 sitepackages = True