rhel-osd-director: Post upgrade to 8.0 adding new nodes to the Overlcoud should use 8.0 images.   

Environment:
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instack-undercloud-2.2.5-1.el7ost.noarch
instack-0.0.8-2.el7ost.noarch
openstack-heat-engine-5.0.1-3.el7ost.noarch
openstack-tripleo-heat-templates-kilo-0.8.10-2.el7ost.noarch


Description:
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after the upgrade process is finish, the undercloud and overcloud are in 8.0 version, 
but the images on the undercloud remain in 7.3.  so when we will scale-up, and add a new node to the overcloud post-upgrade, 
the new node will use the 7.3 images on the undercloud. 

we should verify that part of the upgrade process is to build the 8.0 newer-images and re-upload them using glance to replace the older 7.3 images.