Merge pull request #5471 from dex4er/feature_etc_default_gitlab

Read configuration variable file (/etc/default/gitlab) if it is present

lib/support/init.d/gitlab

@@ -31,6 +31,8 @@ sidekiq_pid_path="$pid_path/sidekiq.pid"
 ### Here ends user configuration ###
+# Read configuration variable file if it is present
+test -f /etc/default/gitlab && . /etc/default/gitlab
 # Switch to the app_user if it is not he/she who is running the script.
 if [ "$USER" != "$app_user" ]; then