Use WP_Rewrite::set_permalink_structure instead of plain update_option() in...

Use WP_Rewrite::set_permalink_structure instead of plain update_option() in populate_network(). Fixes #20174.

This has the benefit of calling WP_Rewrite::init() which correctly resets the permalink_structure
property of the $wp_rewrite global so that the rewrite rules generated on the next flush are correct.


git-svn-id: https://core.svn.wordpress.org/trunk@20117 1a063a9b-81f0-0310-95a4-ce76da25c4cd