[2/3] Add "vlanid" to VLAN information

Currently vdsm does not report vlan id as an idependent field. ovirt-engine
is deducting vlan id by parsing vlan name, not reasonable as vlans can be
made with any name.
This patch adds the 'vlanid' information for vlans to be consumed by
ovirt-engine:

...
        vlans = {'eth0.10': {'addr': '',
                             'cfg': {},
                             'iface': 'eth0',
                             'ipv6addrs': [],
                             'mtu': '1500',
                             'netmask': '',
                             'vlanid': 10},
                 'eth0.myvlan': {'addr': '',
                                 'cfg': {},
                                 'iface': 'eth0',
                                 'ipv6addrs': [],
                                 'mtu': '1500',
                                 'netmask': '',
                                 'vlanid': 20}}

...

Change-Id: I6c83a7639bd4219771df0c7b3dd41b8f9806e9f1
Signed-off-by: Amador Pahim <apahim@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18181
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>