Move bandit to pep8 as generic linting target

bandit is a security linter and can be made voting now. Instead of
starting another virtual machine, run it as part of the generic linting
target which is pep8.

Change-Id: I6a8f7aa2b60bd96d55b37b6cc2a371069d6d5e6a

tox.ini

@@ -29,6 +29,7 @@ commands =
   {toxinidir}/tools/validate-all-yaml.sh
   {toxinidir}/tools/validate-all-dockerfiles.sh
   {toxinidir}/tools/validate-all-file.py
+  bandit -r ansible/library docker kolla tests tools
 
 [testenv:bandit]
 commands = bandit -r ansible/library docker kolla tests tools