Update cryptography library since old version contained security
vulnarability.
@@ -34,7 +34,7 @@ stevedore==1.28.0
paramiko==2.4.1
networkx==1.11
python-keyczar==0.716
-cryptography==2.2.2
+cryptography==2.3.0
retrying==1.3.3
# Note: We use latest version of virtualenv which uses pip 9.0
virtualenv==15.1.0
