Don't include openstack/common in flake8 exclude list

There is no this directory openstack/common which was used
to keep codes from oslo-incubator, we have retired oslo-incubator.
Removing openstack/commonfrom all OpenStack code in favor of the
Oslo libraries is a project wide goal for the Ocata release. So
don't use this directory any more. We should drop it for improving
searching efficiency.

Change-Id: Ia154f7557575351173b9fe646e48bc5210ab698f

Author: gecong1973

tox.ini

@@ -35,7 +35,7 @@ commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasen
 
 [flake8]
 show-source = True
-exclude = .venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build,tools
+exclude = .venv,.git,.tox,dist,doc,*lib/python*,*egg,build,tools
 
 [hacking]
 import_exceptions =