Multisite/network configurations use your current blog as the default…

[danc1248]

Multisite/network configurations use your current blog as the default when using the WP_User_Query which means if a user already exists, from a different blog, you will not find them, but also can't create a new account because they already exist. This overrides your current blog and will search 'all'

All Submissions:

• Have you followed the plugin Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Closes #176.

How to test the changes in this Pull Request:

1. Using a multi-site configuration with two different clients:
2. Login to site A with a new user - the user is created successfully
3. Logout and login to site B. The user is not found but it will fail to create a new user with error "failed-user-creation". The original error is "existing_user_email"
4. With the code changes the user will be found on site B and you will login successfully

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changelog entry

Enter a summary of all changes on this Pull Request. This will appear in the changelog if accepted.

get_user_by_identity uses the current site as the default when searching for a user. This fails to find existing users on a multi-site / network setup. By passing 'blog_id' => 0, it searches all sites.