This patch will add "--vnffgd-template" to vnffg-update command to support
update VNFFG from file. User can run:
tacker vnffg-update --vnffgd-template <vnffgd-file-name> vnffg_name
to update the existing VNFFG.
Partially Implements: blueprint update-vnffg
Change-Id: Ief0469d870530693798f798ecd2f52782318795b