Fixes metadata attributes
Fixes metadata attributes

The way metadata was being sent to google api was wrong. According to
API reference
https://cloud.google.com/compute/docs/reference/latest/instances#resource
metadata items are hashes like this:

{'key': mykey, 'value': myvalue}

However they were being passed as:

{'mykey': 'myvalue'}

mbrukman/knife-google,paulrossman/knife-google,scottmcmaster/knife-google,nullbus/knife-google,ClogenyTechnologies/knife-google,philoserf/knife-google,chef/knife-google,chef/knife-google