Docker: fix redis config, create /var/log/skynet

[rsbohn]

When I tried to run Skynet in Docker I got a few errors. With this patch I was able to run it.

• create /var/log/skynet
• in the config.js.docker (skynet config) match the redis settings to what the redis module expects.

Tested:

• build a new Docker image
• launch the image (docker run -i -t -p 3000 skynet:latest)
• create a new device in the localhost skynet
• use 'curl -X PUT' to update the device

[chrismatthieu]

Thank you!