Implemented scaling VNF feature.
* POST /vnflcm/v1/vnf_instances/{vnfInstanceId}/scale
Implements: blueprint support-etsi-nfv-specs
Spec: https://specs.openstack.org/openstack/tacker-specs/specs/victoria/support-scale-api-based-on-etsi-nfv-sol.html
Change-Id: Ief7d52af908581c00939b3c6c23de7c85ea5f7cf
(cherry picked from commit e8623c1df0)