Manually delete fixture in `test_mysqli_flush_sync()`.

This test creates a dummy post and subsequently runs a query containing
`DROP PROCEDURE`. This latter query implies a `COMMIT`, which means that the
post is not cleaned up for later tests. Manually deleting the post with
`wp_delete_post()` solves this problem.

Fixes #28155.
Built from https://develop.svn.wordpress.org/trunk@30320


git-svn-id: http://core.svn.wordpress.org/trunk@30319 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.1-alpha-30319';
+$wp_version = '4.1-alpha-30320';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.