Introduce container_registry for image prefix

Skip-Release-Notes
Change-Id: I80067f53aa2b63286b654fff782f0f7b65a2d050
diff --git a/images/placement/Dockerfile b/images/placement/Dockerfile
index 644737b..ad0290a 100644
--- a/images/placement/Dockerfile
+++ b/images/placement/Dockerfile
@@ -1,9 +1,10 @@
 # SPDX-License-Identifier: Apache-2.0
 # Atmosphere-Rebuild-Time: 2024-06-25T22:49:25Z
 
+ARG REGISTRY
 ARG RELEASE
 
-FROM harbor.atmosphere.dev/library/openstack-venv-builder:${RELEASE} AS build
+FROM ${REGISTRY}/openstack-venv-builder:${RELEASE} AS build
 ARG PLACEMENT_GIT_REF=b3652feea1855c9481c9441976379d9851c0c62f
 ADD --keep-git-dir=true https://opendev.org/openstack/placement.git#${PLACEMENT_GIT_REF} /src/placement
 RUN git -C /src/placement fetch --unshallow
@@ -13,5 +14,5 @@
         /src/placement
 EOF
 
-FROM harbor.atmosphere.dev/library/openstack-python-runtime:${RELEASE}
+FROM ${REGISTRY}/openstack-python-runtime:${RELEASE}
 COPY --from=build --link /var/lib/openstack /var/lib/openstack