Prevent systematic download when tests are executed in Docker

[bgaillard]

When we run the embedded server using the Gomoob phptools Docker container it first download a Mongo DB distribution and installs it.

It works but because the Docker container used to run tests is ephemeral each time tests are run again the dowload it performed.

We should document how to run the server inside Docker by mapping the directory where the Mongo distribution are downloaded and installed.