Update names of Rsyslog container Image variables
Update names of Rsyslog container Image variables

Names used in rsyslog-container-puppet.yaml, with "Docker"
were outdated. Correct names are with "Container" instead of
"Docker" and this commit updates that.

Change-Id: Id599d3d121926c66c190f299094b53b484175d35

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates