Add support for flat networks in SRIOV Mechanism Driver

Allow flat network segment to be bound by SRIOV Mechanism Driver.
Populate vif_details with vlan_id = 0 to support flat networking
(according to man page of ip command).

Change-Id: Ibbe2db51ed370f416e81d90d203049e7c39eff5b
Closes-Bug: 1403626
Merge "Add support for flat networks in SRIOV Mechanism Driver"