Remove *.pyc files before running tox tests
Remove *.pyc files before running tox tests

Modified tox.ini to remove any .pyc file before running tests.
Also, now it removes all the __pycache__ folders which was also
in the bug report.

Change-Id: I2f60751b155f8098b746339c12406b934bcdbcf9
Closes-Bug: #1525852

openstack/watcher,openstack/watcher,stackforge/watcher,stackforge/watcher