chore(controller): update paramiko to 1.15.2

See paramiko/paramiko@v1.14.1...v1.15.2

Author: mboersma

requirements.txt

@@ -12,7 +12,7 @@ django-json-field==0.5.7
 djangorestframework==2.4.4
 docker-py==0.6.0
 gunicorn==19.1.1
-paramiko==1.14.1
+paramiko==1.15.2
 psycopg2==2.5.4
 python-etcd==0.3.2
 PyYAML==3.11