get_blog_option queries DB on default blog_id

[wpmuguru]

If get_blog_option is passed null for a blog_id, it queries the DB instead of using the current blog option cache.

In most, if not all, of the MS specific functions that have a $blog_id, if $blog_id is null, the current blog is used.

patch is attached.

[wpmuguru]

The $wpdb->get_blog_prefix( ... will return the prefix for the current blog when null is passed. So, the current implementation defaults to the current blog but queries the DB instead of retrieving from cache.

[nacin]

Added test cases for a slew of changes about to drop: ​[UT436].

[nacin]

In [18662]:

Allow get_blog_option(null,...) to hit the cache for the current blog. New return values for add_blog_option, update_blog_option, delete_blog_option. Don't set the cache in those functions if add/update/delete_option failed. see #17883.

[nacin]

Sorry wpmuguru, tried to stop the commit to include props. Thanks for the contribution as always :-)

[nacin]

Leaving this open so ryan can review it.

[wpmuguru]

Replying to nacin:

Sorry wpmuguru, tried to stop the commit to include props. Thanks for the contribution as always :-)

No problem - I've done the same.