Are you surprised why your mysql user-password is not working after upgradation to newer version of mysql server. Yes, It will not allow you to login in mysql server this way. Answer is simple: Just change your mysql password using old_password() function.
mysql> Set password = old_password('password');
This will change current user's password only.
mysql> Set password for 'user1'@'ur_host' = old_password('password');
This will change password for "user1".