ci: improve image-manifest reliability (#981)

diff --git a/roles/defaults/vars.go b/roles/defaults/vars.go
index 4dc1e7d..4c11748 100644
--- a/roles/defaults/vars.go
+++ b/roles/defaults/vars.go
@@ -12,6 +12,20 @@
 	varsFile []byte
 )
 
+func GetImages() (map[string]string, error) {
+	path, err := yaml.PathString("$._atmosphere_images")
+	if err != nil {
+		return nil, err
+	}
+
+	var images map[string]string
+	if err := path.Read(bytes.NewReader(varsFile), &images); err != nil {
+		return nil, err
+	}
+
+	return images, nil
+}
+
 func GetImageByKey(key string) (string, error) {
 	path, err := yaml.PathString("$._atmosphere_images." + key)
 	if err != nil {