Security group rules in module openstack.cloud.security_group
are changed/updated only when option 'security_group_rules' was
defined explicitly. This follows our policy of "apply no change"
when module options in our Ansible modules have not been set.
Story: 2010691
Task: 47795
Change-Id: I4a0cda46cb160b5321913b63ff1123d8b8a19705