Ensure that a request URL is always set in `WP_UnitTestCase::go_to()`.

Failure to set this variable meant that passing the home URL to `go_to()`
(without a trailing slash) resulted in a PHP notice, and failed to reset the
globals properly.

Props joostdevalk.
Fixes #31417.
Built from https://develop.svn.wordpress.org/trunk@31515


git-svn-id: http://core.svn.wordpress.org/trunk@31496 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31514';
+$wp_version = '4.2-alpha-31515';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.