Feature 7106 : Handle additional EPA parameters for openstack VIM connector

Gerrit feature request : https://osm.etsi.org/gerrit/#/c/7106/



Changes:

NFVO engine to read and parse the quota descriptor and store as flavor extended properties.

Openstack VIM Connector to process the new extended properties and suitably pass them as extra specs when creating flavor.

Change-Id: Icdd8730f6f6de6d420027de962f0f5def0376375
Signed-off-by: anwars <anwars@vmware.com>