Prevent index.html from mounted location being over-written by entrypoint script

[KamranAzeem]

The default index.html is great for testing, but if one mounts some web-content directory on the default nginx webroot, the docker-entrypoint.sh overwrites the index.html file there. This is undesired.

The entrypoint script should check if the index.html exists already, then it should not overwrite it. Instead, it should show the index.html from mounted content.

[KamranAzeem]

Fixed in 5c97d80