(QENG-407) update google compute to differentiate between template and platform

- assume that the google compute image name will be in host[:image],
  otherwise default to host[:platform]
- fixes up the differentiations between google naming rules and our
  internal platform naming rules
firewall + ssh fixes for google compute

- firewall allows ports 8080/8081
- retry on failure to authenticate errors (happens when google compute
  boxes haven't successfully spun up yet)
Merge pull request #197 from anodelman/google-cloud

(QENG-407) update google compute to differentiate between template and platform