Solve letsencrypt ssl error

For more information watch here : plesk/letsencrypt-plesk#117

Before error was like this : 

```
pkg_resources.ContextualVersionConflict: (cryptography 1.8.1 (/usr/lib/python2.7/site-packages), Requirement.parse('cryptography>=2.1.4'), set(['PyOpenSSL']))
```

scripts/spcgeonode/letsencrypt/Dockerfile

@@ -1,7 +1,7 @@
 FROM alpine:3.6
 
 # 1-2. Install system dependencies
-RUN apk add --no-cache certbot
+RUN apk add --no-cache certbot py-pip && pip install pyopenssl==16.0.0
 
 # Installing scripts
 ADD docker-entrypoint.sh /docker-entrypoint.sh