Multithreaded resync of vnc_cfg_api for openstack

This commit adds a threading pool of workers to handle
create/delete tenants.

Change-Id: I3f3ffd5434e1a1bba985911290d3f181ee1155d7
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@cloudwatt.com>
Merge "Multithreaded resync of vnc_cfg_api for openstack"