Port list takes to much times to return

When a classic user list ports without any filters, the command takes
too much time to return.

Signed-off-by: Édouard Thuleau <edouard.thuleau@cloudwatt.com>

Conflicts:
	neutron_plugin_contrail/plugins/opencontrail/ctdb/config_db.py
Merge pull request #23 from cloudwatt/list_port_to_long

Port list takes to much times to return