new user with same name as a before deleted one inherits personal info

[mind22]

Steps to reproduce

1. Create new test account
2. Login and upload picture + create personal infos + Logout
3. Delete test account
4. Create test account with same name but different (or same) password

Expected behaviour

I think this should be handled as a new account.

Actual behaviour

The test account in step 4. inherits the personal infos and profile picture from the one filled in step 2.

Server configuration

Operating system: Ubuntu Server 16.04.2 LTS

Web server: nginx 1.10.0

Database: mysql 10.0.29

PHP version: 7.0.15

Nextcloud version: 11.0.3

Updated from an older Nextcloud/ownCloud or fresh install: Updated from 11

Where did you install Nextcloud from: official homepage

[MorrisJobke]

similar to #1557

cc @nickvergessen @rullzer @ChristophWurst