Update gcloud CLI on our images

[cotsog]

We've received a request to have gcloud updated on our images. Right now we provide version 154.0 while the latest is 171.0.

Right now it seems to add close to 2 minutes to builds that are updating it manually with a recipe similar to the following:

before_install:
  - export CLOUD_SDK_REPO="cloud-sdk-$(lsb_release -c -s)"
  - echo "deb http://packages.cloud.google.com/apt $CLOUD_SDK_REPO main" | sudo tee -a /etc/apt/sources.list.d/google-cloud-sdk.list
  - curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
  - sudo apt-get update
  - sudo apt-get install google-cloud-sdk google-cloud-sdk-app-engine-java

Unfortunately, this type of installation cannot be cached if I'm not wrong.

Thank you!