netmodels: Improve getIpConfig using namedtuple

Change-Id: I53eb3c4b00f33285a1b299ca0adc6611eb99a989
Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/18167
Reviewed-by: Giuseppe Vallarelli <gvallare@redhat.com>
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Assaf Muller <amuller@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>