anonymous users - remove password checks

[grooverdan]

For anonymous users, those with user='', having a recommendation
to set their passwords, and warning that the password is the same
as the username is a little excessive since there's already a
recommendation to drop the user.

So let's remove those recommendation so we don't see:

[!!] User '@localhost' has user name as password.
[!!] User '@localhost.localdomain' has user name as password.

or:

Set up a Secure Password for @localhost user: SET PASSWORD FOR ''@'SpecificDNSorIp' = PASSWORD('secure_password');
Set up a Secure Password for @localhost.localdomain user: SET PASSWORD FOR ''@'SpecificDNSorIp' = PASSWORD('secure_password');

Lets keep the focus on:
-------- Security Recommendations ------------------------------------------------------------------
[!!] User ''@'localhost' is an anonymous account. Remove with DROP USER ''@'localhost';
[!!] User ''@'localhost.localdomain' is an anonymous account. Remove with DROP USER ''@'localhost.localdomain';

[jmrenouard]

Agree with that ;)