Use parent repo credentials for submodule processing

When expanding submodules, rely on the credential ids of the parent
project for fetching securely the submodules.

Change-Id: I6d8fafcd4758d17db3f9f02d9fe63a3c017be135
diff --git a/jenkins/gerrit-sbt-plugin-template.yaml b/jenkins/gerrit-sbt-plugin-template.yaml
index 4c942d7..6d21d99 100644
--- a/jenkins/gerrit-sbt-plugin-template.yaml
+++ b/jenkins/gerrit-sbt-plugin-template.yaml
@@ -28,6 +28,7 @@
             - origin/{branch}
           submodule:
             recursive: true
+            parent-credentials: true
           skip-tag: true
           do-not-fetch-tags: true
     triggers: