Remove $wgDataCenterId/$wgDataCenterRoles

These ended up not getting used after some patch changes

Change-Id: I7c56d58972d1efcca6a249b7fb4d422a4006da88

RELEASE-NOTES-1.27

@@ -96,9 +96,8 @@ production.
   class's methods.
 
 === New features in 1.27 ===
-* $wgDataCenterId and $wgDataCenterRoles where added, which will serve as
-  basic configuration settings needed for multi-datacenter setups.
-  $wgDataCenterUpdateStickTTL was also added.
+* $wgDataCenterUpdateStickTTL was also added. This decides how long a user
+  sticks to the primary DC (via cookies) after they make changes to the site.
 * Added a new hook, 'UserMailerTransformContent', to transform the contents
   of an email. This is similar to the EmailUser hook but applies to all mail
   sent via UserMailer.

includes/DefaultSettings.php

@@ -1871,24 +1871,6 @@ $wgDBservers = false;
  */
 $wgLBFactoryConf = array( 'class' => 'LBFactorySimple' );
 
-/**
- * The ID of the current data center
- * @since 1.27
- */
-$wgDataCenterId = 'default';
-
-/**
- * Map of data center IDs to their role ("master" or "slave")
- *
- * Multiple data centers can be setup to handle MediaWiki, with HTTP
- * POSTs routed to the master data center and GET/HEAD/OPTION routed to
- * any data center (usually the closest to the end user). In such setups,
- * this setting should be set to the appropriate value in the site
- * config for each data center.
- * @since 1.27
- */
-$wgDataCenterRoles = array( 'default' => 'master' );
-
 /**
  * After a state-changing request is done by a client, this determines
  * how many seconds that client should keep using the master datacenter.