Release process: add a sudo call

It's better to have sudo ask for a password upfront than letting the
wrapper start children which might lead to entangled sudo prompt and
log lines.

wiki/src/contribute/release_process.mdwn

@@ -943,6 +943,7 @@ before starting the wrapper from `puppet-tails`:
        PUPPET_TAILS_REMOTE=$(echo -n "${TAILS_REMOTE?:}" | perl -p -E 's,:tails(:?[.]git)?\z,:puppet-tails,')
        cd "${WORK_DIR?:}"
        git clone "$PUPPET_TAILS_REMOTE"
+       sudo -l
        ./puppet-tails/files/jenkins/slaves/isobuilders/wrap_tails_create_iuks \
            --tails-git-remote "file://${RELEASE_CHECKOUT?:}/.git"             \
            --tails-git-commit "${TAG?:}"                                      \