Run the Deploy step as root

Running as the default user Jenkins uses it doesn’t seem to have access to
wherever the artifacts from the previous steps get stored, so it fails to
extract them. Hopefully running as root will let it access them.

Jenkinsfile

@@ -34,6 +34,7 @@ pipeline {
             agent {
                 docker {
                     image 'instrumentisto/rsync-ssh'
+                    args '-u root --privileged'
                 }
             }