virsh: topology extend number count
virsh: topology extend number count

In multi hypervisor implementation, request to extend nodes is
considered as totoal number of nodes instead of appending that
to existing node count i.e
1) ir --topology-nodes compute:3
2) ir virsh --topology-nodes compute:5 --topology-extend True
step 1 is creating 3 nodes in hypervisor and step 2 is adding two more
nodes to make the count to 5. With this the hypervisor will have
5 nodes instead of 8 nodes. In this change we fix it, so that
hypervisor will have have 8 nodes instead of 5 nodes.

GH-2689

Change-Id: Ib40c1bfd8f5fcef7f0d2475fbae1243dbc36fadc

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared