[#1633] Fix delayed creation of unix user.


Problem description
===================

It looks like pwd.getpwnam might also raise KeyError.

```
user = pwd.getpwnam(name_encoded)
KeyError: 'getpwnam(): name not found: m\xc3\xa2\xc8\x9b mi\xc8\x9bi\xc8\x99or'
```


Changes description
===================

Update code to catch KeyError when waiting for account to be created.

Rename method name to be the same format as for group creation method.


How to try and test the changes
===============================

reviewers @alibotean 

This is just to let you know about the change.

Hope this will reduce the number of  random failures.

Thanks!