OPENDEV: Introduce ssh key with passphrase for push-upstream job

Change-Id: If2ef84c27e787c4a780e8c8a11357e699f7c3406
diff --git a/jjb/opendev/global-templates-opendev-push-upstream.yaml b/jjb/opendev/global-templates-opendev-push-upstream.yaml
index af374e4..cabc612 100644
--- a/jjb/opendev/global-templates-opendev-push-upstream.yaml
+++ b/jjb/opendev/global-templates-opendev-push-upstream.yaml
@@ -34,6 +34,9 @@
     wrappers:
       - build-timeout:
           timeout: 10
+      - ssh-agent-credentials:
+          users:
+            - 'infra-upstream-gerrit-ssh-passphrase'
 
     builders:
       - shell: