Remove overcloud-agent element from overcloud images

Configuration has been entirely ansible driven for a few releases, so
no os-collect-config or python3-heat-agent packages need to be
installed now.

Change-Id: I9ec594beca06dba18ffeee44f9ce9457a2ce829c

image-yaml/overcloud-hardened-images-uefi-python3-rt-kernel.yaml

@@ -4,7 +4,6 @@ disk_images:
     type: qcow2
     elements:
       - openvswitch
-      - overcloud-agent
       - overcloud-base
       - overcloud-controller
       - overcloud-compute

image-yaml/overcloud-hardened-images-uefi-python3.yaml

@@ -4,7 +4,6 @@ disk_images:
     type: qcow2
     elements:
       - openvswitch
-      - overcloud-agent
       - overcloud-base
       - overcloud-controller
       - overcloud-compute

image-yaml/overcloud-images-ceph.yaml

@@ -4,7 +4,6 @@ disk_images:
     type: qcow2
     elements:
       - baremetal
-      - overcloud-agent
       - overcloud-base
       - overcloud-ceph-storage
       - puppet-modules

image-yaml/overcloud-images-python3.yaml

@@ -5,7 +5,6 @@ disk_images:
     elements:
       - baremetal
       - openvswitch
-      - overcloud-agent
       - overcloud-base
       - overcloud-controller
       - overcloud-compute

image-yaml/overcloud-realtime-compute-python3.yaml

@@ -5,7 +5,6 @@ disk_images:
     elements:
       - baremetal
       - openvswitch
-      - overcloud-agent
       - overcloud-compute
       - puppet-modules
       - stable-interface-names