Now each user item may or may not have a groups attribute. The
groups attribute is a comma separated list of group names. If
present the first group name will be the login or primary group,
if not present, the underlying toolchain will assign the default
login group for that user.
At the moment there is no class to build the pxe client config
file from information provided with the optional pxedeploy
section. However this is not fatal to the build because the file
could be created manually too. Thus a warning message is shown
which will go away when the pxe client config file creation
has been ported
