Don't delete posts when we delete users

[joshbetz]

We need to make sure that we don't delete existing posts when we delete users, including when we delete any existing users in User::add.

https://github.com/Automattic/vip-support/blob/master/class-vip-support-user.php#L930

[mjangda]

Why would a Support User have posts on a site that should be kept?

[hrkhal]

@mjangda / @joshbetz Because said support user used to work here for us and in his time here he imported articles from a previous CMS into our WordPress site under his own WordPress user.