Bandit: add B311 to skiplist

Bandit 1.8.4 is more strict for random functions, see: [1],
to avoid pep8 failures due to the few random calls in Neutron,
skip B311

[1]: https://github.com/PyCQA/bandit/releases/tag/1.8.4

Change-Id: I1a2119221be57afaa94a94ecb1448196802f041b

Author: elajkat

tox.ini

@@ -279,7 +279,9 @@ description =
     Run bandit security checks.
 deps = {[testenv:pep8]deps}
 # B104: Possible binding to all interfaces
-commands = bandit -r neutron -x tests -n5 -s B104
+# B311: Standard pseudo-random generators are not suitable for
+#       security/cryptographic purposes
+commands = bandit -r neutron -x tests -n5 -s B104,B311
 
 [testenv:bashate]
 description =