install.sh reports successful user creation, but not really

During ```install.sh```, the installer asks for a username and password. If the username already exists, it reports the following: 

```
ERROR 1396 (HY000) at line 1: Operation CREATE USER failed for 'test'@'localhost'
User successfully created!
```

This could be handled more gracefully.

Additional things to check: 
  - if the username is given a new password, does it change?