Need to actually expand the variables

inventory/group_vars/all

@@ -81,8 +81,8 @@ virt_install_command_rhel6: /usr/sbin/virt-install -n {{ inventory_hostname }}
                   hostname={{ inventory_hostname }}" 
                  --network=bridge=br0 --autostart --noautoconsole --watchdog default
 
-max_mem_size: mem_size * 5
-max_cpu: num_cpus * 5
+max_mem_size: "{{ mem_size }} * 5"
+max_cpu: "{{ num_cpus }} * 5"
 
 # This is the wildcard certname for our proxies.  It has a different name for
 # the staging group and is used in the proxies.yml playbook.