Fix lxc_hosts_container_image_url condition
Fix lxc_hosts_container_image_url condition

lxc_hosts_container_image_url is string, so can't be passed through bool
filter as it will always result as false.

Change-Id: I0f12760840d81c9d73118d63bc0927eab78b9df2
Closes-Bug: #1908544

openstack/openstack-ansible-lxc_hosts,openstack/openstack-ansible-lxc_hosts