Merge branch 'da-fix-issue-2603' into 'master'

Check if database_geo.yml exist before setting the tracking DB config

Closes #2603

See merge request !2071

config/initializers/geo.rb

-if Gitlab::Geo.secondary_role_enabled?
+if File.exist?(Rails.root.join('config/database_geo.yml')) &&
+    Gitlab::Geo.secondary_role_enabled?
   Rails.application.configure do
     config.geo_database = config_for(:database_geo)
   end