baremetal: Use CACHEURL for ipa/rhcos images

This allows for optional caching of the images on the host running
the bootstrap VM, which is particularly useful when developing
to save time and bandwidth, and potentially also for offline installs
in future.

data/data/bootstrap/baremetal/files/usr/local/bin/startironic.sh

@@ -71,9 +71,11 @@ podman run -d --net host --privileged --name httpd \
      -v $IRONIC_SHARED_VOLUME:/shared:z --entrypoint /bin/runhttpd ${IRONIC_IMAGE}
 
 podman run -d --net host --name ipa-downloader \
+     --env CACHEURL="http://172.22.0.1/images" \
      -v $IRONIC_SHARED_VOLUME:/shared:z ${IPA_DOWNLOADER_IMAGE} /usr/local/bin/get-resource.sh
 
 podman run -d --net host --name coreos-downloader \
+     --env CACHEURL="http://172.22.0.1/images" \
      -v $IRONIC_SHARED_VOLUME:/shared:z ${COREOS_DOWNLOADER_IMAGE} /usr/local/bin/get-resource.sh $RHCOS_IMAGE_URL
 
 # Start the conductor so db sync can happen while images download