Clarify some variable names in glance discovery
Clarify some variable names in glance discovery

I'm bad at naming things. This was unreadable. Update the variable names
so it makes sense and add a comment.

Change-Id: Iacbaeed91d71dca35c6fdd7d07999bd5956430fa

openstack/python-openstacksdk,dtroyer/python-openstacksdk,openstack/python-openstacksdk,dtroyer/python-openstacksdk,stackforge/python-openstacksdk,openstack-infra/shade,openstack-infra/shade,stackforge/python-openstacksdk