Fix typo in the bookshelf GCE example - #167

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I signed it!

CLAs look good, thanks!

It looks like there's some problems in gce/startup-script.sh too; the jetty URL there no longer exists, and the service code assumes a System V Init, but the machine that's used now uses systemd. I have patches for that too but I wasn't sure whether it was better to try to use an older Debian image or to update it to use systemd

Closing because #168 fixes more problems