8021Qbh: use preassociate-rr during the migration prepare stage

8021Qbh: use preassociate-rr during the migration prepare stage

This patch introduces PREASSOCIATE-RR during incoming VM migration on the
destination host. This is similar to the usage of PREASSOCIATE during
migration in 8021qbg libvirt code today. PREASSOCIATE-RR is a VDP operation.
With the latest at IEEE, 8021qbh will need to support VDP operations.
A corresponding enic driver patch to support PREASSOCIATE-RR for 8021qbh
will be posted for net-next-2.6 inclusion soon.