Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1503834

Description of problem:
the pxeloader option is not properly inherited from the parent host group and stays at 'no value'.

Version-Release number of selected component (if applicable):
6.3.0-20

Steps to Reproduce:
1. create a host group, choose some OS and some PXEloader
2. create a nested host group and check its pxeloader option

Actual results:
Inherit (no value)

Expected results:
Inherit (the parent hg pxeloader value)