Change of ConfigWriter._createConfFile parameters

ifcfg.ConfigWriter._createConfFile now accepts _ipConfig object instead
of number of arguments. It helps to reduce number of arguments passed

Change-Id: Iae5ec15048ed52170371dda1d0fa9b90d51838e3
Signed-off-by: Petr Sebek <psebek@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18331
Reviewed-by: Dan Kenigsberg <danken@redhat.com>