Prevent Multisite term tests from hitting database for 'db_version'.

[34718] introduced a 'db_version' check to term meta functions, to ensure that
they don't run when the term meta schema is not yet in place. This call to
`get_option()` causes a database hit during Multisite tests, due to the
presence of the `WP_INSTALLING` constant. See #31130. The extra database
queries are causing cache tests to fail.

In similar cases, we have `markTestSkipped()` when `is_multisite()`. Because
the term meta API is so extensive - term meta caches can be primed anywhere a
`WP_Query` loop is fired up - we implement a more generous workaround in this
case. To prevent `get_option( 'db_version' )` from hitting the database during
multisite unit tests, we use a 'pre_option_' filter.

Heaven help us.

See #34091.
Built from https://develop.svn.wordpress.org/trunk@34719


git-svn-id: http://core.svn.wordpress.org/trunk@34683 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-34718';
+$wp_version = '4.4-alpha-34719';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.