pipeline-utils: add prep_container_storage()

This re-implements some of what is contained in
`scripts/pull-mount-oscontainer` to allow parts of the pipeline to
pull container images from inside another container.

pipeline-utils.groovy

@@ -143,6 +143,17 @@ def registry_login(username, password, registry) {
     sh "podman login -u '${username}' -p '${password}' ${registry}"
 }
 
+// re-implementation of some functionality from scripts/pull-mount-oscontainer
+// sets up local container storage so the pipeline can pull container images
+// from inside another container
+def prep_container_storage(hostStorage, localStorage) {
+    sh """
+        rm -rf ${localStorage}
+        mkdir -p ${localStorage}
+        rm -rf ${hostStorage} && mkdir -p ${hostStorage}
+        mount --bind ${localStorage} ${hostStorage}
+    """
+}
 // Substitute secrets from credentials into files in the git repo
 def prepare_configuration() {
     withCredentials([