WP_Query should use WP_Query::is_admin, not is_admin(), to add protected statuses

[nacin]

WP_Query sets up an WP_Query::is_admin flag based on is_admin() in WP_Query::parse_query(). But it never uses it. When it goes to add protected post statuses, it checks is_admin() again.

To allow this to be easily filtered from the parse_query hook (something I plan to submit to the Debug Bar Console, as it uses admin-ajax which thinks it is is_admin), we should be using the query flag, not the function.

[ryan]

Looks good.

[nacin]

In [19932]:

Use is_admin WP_Query propery, not is_admin(), when adding protected post statuses to the query. Allows for overriding on the parse_query hook. fixes #20049.