anonymous users - remove password checks

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';

Author: grooverdan

mysqltuner.pl

@@ -1819,12 +1819,14 @@ sub security_recommendations {
     if ( mysql_version_ge(10, 4) ) {
         @mysqlstatlist = select_array
 q{SELECT CONCAT(user, '@', host) FROM mysql.global_priv WHERE
-    JSON_CONTAINS(Priv, '"mysql_native_password"', '$.plugin') AND JSON_CONTAINS(Priv, '""', '$.authentication_string')
+    user != ''
+    AND JSON_CONTAINS(Priv, '"mysql_native_password"', '$.plugin') AND JSON_CONTAINS(Priv, '""', '$.authentication_string')
     AND NOT JSON_CONTAINS(Priv, 'true', '$.account_locked')};
     }
     else {
         @mysqlstatlist = select_array
 "SELECT CONCAT(user, '\@', host) FROM mysql.user WHERE ($PASS_COLUMN_NAME = '' OR $PASS_COLUMN_NAME IS NULL)
+    AND user != ''
     /*!50501 AND plugin NOT IN ('auth_socket', 'unix_socket', 'win_socket', 'auth_pam_compat') */
     /*!80000 AND account_locked = 'N' AND password_expired = 'N' */";
     }
@@ -1852,7 +1854,7 @@ sub security_recommendations {
 
     # Looking for User with user/ uppercase /capitalise user as password
     @mysqlstatlist = select_array
-"SELECT CONCAT(user, '\@', host) FROM mysql.user WHERE CAST($PASS_COLUMN_NAME as Binary) = PASSWORD(user) OR CAST($PASS_COLUMN_NAME as Binary) = PASSWORD(UPPER(user)) OR CAST($PASS_COLUMN_NAME as Binary) = PASSWORD(CONCAT(UPPER(LEFT(User, 1)), SUBSTRING(User, 2, LENGTH(User))))";
+"SELECT CONCAT(user, '\@', host) FROM mysql.user WHERE user != '' AND (CAST($PASS_COLUMN_NAME as Binary) = PASSWORD(user) OR CAST($PASS_COLUMN_NAME as Binary) = PASSWORD(UPPER(user)) OR CAST($PASS_COLUMN_NAME as Binary) = PASSWORD(CONCAT(UPPER(LEFT(User, 1)), SUBSTRING(User, 2, LENGTH(User)))))";
     if (@mysqlstatlist) {
         foreach my $line ( sort @mysqlstatlist ) {
             chomp($line);