Add Geo config using from_file instead of blockinfile

Current problem

Rerunning all.yml on a Geo deployment will completely overwrite the gitlab.rb file on all machines and remove the Geo specific config.

Solution

By using from_file we can have the main gitlab.rb look for other configs to load in. This allows the all.yml to control the main gitlab.rb file without altering config that was added after the initial run.