if username is present, display "send reset password" link

Display a "send reset password email" link for any record containing a non-empty username value.

At present, there is a lot of logic surrounding what message to display here ("create credentials" vs "reset credentials") but this logic relies on an insecure endpoint that will soon be removed (MODLOGIN-128). Since we send the same "reset your password" message regardless of the text of the link on the user-edit page, there's no reason for all that effort; when a username is present, display a "send reset password email" link, end of story.