mtr: set @skip_auth_anonymous=1 (#538)

Since 736afe86 the
mysql_system_tables_data.sql only installs the anonymous
user if skip_auth_anonymous IS NULL.

Its installation is prevented by setting this to 1.

mysql-test/mysql-test-run.pl

@@ -3198,6 +3198,9 @@ sub mysql_install_db {
       mtr_appendfile_to_file("$sql_dir/mysql_performance_tables.sql",
                             $bootstrap_sql_file);
 
+      # Don't install anonymous users
+      mtr_tofile($bootstrap_sql_file, "set \@skip_auth_anonymous=1;\n");
+
       # Add the mysql system tables initial data
       # for a production system
       mtr_appendfile_to_file("$sql_dir/mysql_system_tables_data.sql",
@@ -3232,10 +3235,6 @@ sub mysql_install_db {
            sql_to_bootstrap($text));
     }
 
-    # Remove anonymous users
-    mtr_tofile($bootstrap_sql_file,
-         "DELETE FROM mysql.user where user= '';\n");
-
     # Create mtr database
     mtr_tofile($bootstrap_sql_file,
          "CREATE DATABASE mtr CHARSET=latin1;\n");