drop formatting vars in processed image.yaml files

Fedora CoreOS is the only one today using the variable replacement
in the image.yaml files (see [1]). Fedora CoreOS is also moved over
to building via container so it's not using the code here in COSA
to generate the image.json (uses build-rootfs code instead).

Let's drop this formatting code for now to simplify.

[1] https://github.com/coreos/fedora-coreos-config/blob/286f84bbcc9b233ad065287845b6e21bb0bef306/image-base.yaml#L38

Author: dustymabe

src/cmdlib.sh

@@ -228,7 +228,7 @@ prepare_build() {
     fi
 
     export image_json="${tmp_builddir}/image.json"
-    write_image_json "${image}" "${image_json}" "${manifest}"
+    write_image_json "${image}" "${image_json}"
     # These need to be absolute paths right now for rpm-ostree
     composejson="$(readlink -f "${workdir}"/tmp/compose.json)"
     export composejson
@@ -1084,12 +1084,11 @@ print('Build ${buildid} was inserted ${arch:+for $arch}')")
 write_image_json() {
     local srcfile=$1; shift
     local outfile=$1; shift
-    local ostree_manifest=$1; shift
     (python3 -c "
 import sys
 sys.path.insert(0, '${DIR}')
 from cosalib import cmdlib
-cmdlib.write_image_json('${srcfile}', '${outfile}', ostree_manifest='${ostree_manifest}')")
+cmdlib.write_image_json('${srcfile}', '${outfile}')")
 }
 
 # API to prepare image builds.

src/cosalib/cmdlib.py

@@ -523,16 +523,15 @@ def cmdlib_sh(script):
     '''])
 
 
-def generate_image_json(srcfile, ostree_manifest):
-    manifest_vars = yaml.safe_load(open(ostree_manifest))['variables']
+def generate_image_json(srcfile):
     r = yaml.safe_load(open("/usr/lib/coreos-assembler/image-default.yaml"))
-    for k, v in flatten_image_yaml(srcfile, format_args=manifest_vars).items():
+    for k, v in flatten_image_yaml(srcfile).items():
         r[k] = v
     return r
 
 
-def write_image_json(srcfile, outfile, ostree_manifest):
-    r = generate_image_json(srcfile, ostree_manifest)
+def write_image_json(srcfile, outfile):
+    r = generate_image_json(srcfile)
     with open(outfile, 'w') as f:
         json.dump(r, f, sort_keys=True)