Update google-compute-engine driver to reflect recent API changes

GCE recently added shutdown ability for its instances. When an instance is in shutdown state, a REST API call to the instance returns no STATE information and common operations like listNodes() fail showing a null exception while parsing INPUT for "status".

Could this be fixed so as to ignore stopped instances or atleast not crash any calls made using jclouds.

ps: There also seems to be something funny at the GCE backend. If I stop an instance and fetch node metadata usign Jclouds, I get a terminated for the node, which is what is expected. After say, an hour or so, it no longer returns anything and crashes the call throwing the same error described above.

I'd like to know if this error is replicated on another cloud account.