add support for sequence numner in the VPC topology updates and VPC
routing policy updates

Conflicts:
	setup/db/db/schema-430to440.sql
fix KVM plug-in for OVS tunnel network. Fix addreses two issues.

fix  mismatch of ovs-host-setup, ovs_host_setup used Libvirt resource and
scripts

plug the nic to OVS bridges created for the tunnel network.

Conflicts:
	plugins/hypervisors/kvm/src/com/cloud/hypervisor/kvm/resource/OvsVifDriver.java
CLOUDSTACK-6505: XenServer bridge for the OVS tunnel network gets reset
on the hosts in the xenserver cluster

this fix ensures that brige is created only once so that openflow rules
configured on the bridge are not lost.
CLOUDSTACK-6507: ensure sequence numbers are honoured while processing
OvsVpcPhysicalTopologyConfigCommand and OvsVpcRoutingPolicyConfigCommand

fix ensures only latest updates are applied (new openflow rules) to the
bidge enabled for distributed routing.
incorporate change in getGuestNicModel signature, while handling OVS in
OvsVifDriver