Fix the container.cpu is None in cpu_filter
Fix the container.cpu is None in cpu_filter

Fix container do not specify the --cpu, then cpu_filter will
compare free with None.

Change-Id: I08ba201c405e76b846f36e05a22d97bbe6a4e299

kevin-zhaoshuai/zun,kevin-zhaoshuai/zun,kevin-zhaoshuai/zun