Gitlab logging should honor rails logger configurations

In the current status, gitlab will use the gitlab logger for logging even if a different logger configuration is supplied through rails in config/environments/production.rb This is strange and unexpected behavior since the comments in the environments configuration clearly state that using a different logger should be possible.

  # Use a different logger for distributed setups
  # config.logger = ActiveSupport::TaggedLogging.new(SyslogLogger.new)

This pull request ensures that gitlabs logger honors the configuration given in the environment config, with the small caveat that replying logs will not be possible on anything else than the default configuration. If a different Logger configuration is supplied I think it is reasonable to assume this expected behavior since playback of eg. Syslog is simply not possible.