Update post_install.sh

Author: GyunerZeki

post_install.sh

@@ -121,7 +121,8 @@ WHERE \`id\`='1';
 
 ALTER USER 'roundcube_user'@'127.0.0.1' IDENTIFIED BY '$ROUNDCUBE_MYSQL_PASSWORD';
 ALTER USER 'mailuser'@'%' IDENTIFIED BY '$MYSQL_PASSWORD';
-ALTER USER 'root'@'%' IDENTIFIED BY '$ROOT_MYSQL_PASSWORD';
+GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY '$ROOT_MYSQL_PASSWORD' WITH GRANT OPTION;
+DROP USER root@localhost;
 EOF
 
 # reset generate roundcubemail