Description of problem:
If username in text mode is set to invalid (like j/ohn), anaconda reports that there was error creating user because it already exists. It doesn't

Version-Release number of selected component (if applicable):
Fedora-19-Beta-RC2
anaconda-19.28

How reproducible:
always

Steps to Reproduce:
1. Start installation in text mode
2. create new user, as FULL name enter 'j/ohn', or 'root'
3. Finish installation

Actual results:
10:55:45,378 INFO anaconda: Creating users
10:55:45,379 INFO anaconda: created new libuser.conf at /tmp/libuser.5mTk05 with instPath="/mnt/sysimage"
12:55:45,528 CRIT anaconda: Error when creating new user: name contains invalid char `/'
10:55:45,533 ERR anaconda: User j/ohn already exists, not creating.
10:55:45,535 INFO anaconda: Configuring addons

Expected results:
10:55:45,378 INFO anaconda: Creating users
10:55:45,379 INFO anaconda: created new libuser.conf at /tmp/libuser.5mTk05 with instPath="/mnt/sysimage"
12:55:45,528 CRIT anaconda: Error when creating new user: name contains invalid char `/'
10:55:45,535 INFO anaconda: Configuring addons