Move bandit to pep8

bandit is working fine, move it into pep8 environment to not waste an
extra node usage for running *two* lint like jobs. pep8 is the general
linter job environment and bandit is a security linter.

Once this job is in, the non-voting bandit job for sahara can get
removed from job runs.

Also, add bandit to test-requirements.txt using the version from
global-requirements file.

Change-Id: Ia0ad32666f85d289768f66199c088380ce363b54

test-requirements.txt

@@ -7,6 +7,7 @@ hacking<0.11,>=0.10.0
 Mako>=0.4.0 # MIT
 PrettyTable<0.8,>=0.7 # BSD
 PyMySQL>=0.6.2 # MIT License
+bandit>=0.17.3  # Apache-2.0
 bashate>=0.2 # Apache-2.0
 coverage>=3.6 # Apache-2.0
 doc8 # Apache-2.0

tox.ini

@@ -33,6 +33,8 @@ commands =
     # Run bashate checks
     bash -c "find sahara -iname '*.sh' -print0 | xargs -0 bashate -v"
     bash -c "find devstack -not -name README.rst -and -not -name \*.json -type f -print0 | xargs -0 bashate -v"
+    # Run security linter
+    bandit -c bandit.yaml -r sahara -n5 -p sahara_default
 
 [testenv:venv]
 commands = {posargs}