Special treatment for Oracle

The generated sql statements for oracle (especially trigger statements) need some additional love to be executed consecutive in a script.

@butonic @LukasReschke @icewind1991 please review - THX
```php
 $this->random->generate($13, \OCP\Security\ISecureRandom::CHAR_LOWER.\OCP\Security\ISecureRandom::CHAR_DIGITS);
```