Add ability to store bbl-state in S3/GCS as a tarball

[davewalter]

What is this change about?

This PR updates the bbl-up and bbl-destroy tasks to create tarballs from the bbl-state directory instead of attempting to commit them to a git repository. This allows the tarball to be uploaded to S3 or GCS by a subsequent put step. This is controlled by an optional STORE_BBL_STATE_AS_TARBALL parameter.

Please provide contextual information.

This change is somewhat, but not entirely, related to the request made in this issue: https://github.com/cloudfoundry/cf-deployment-concourse-tasks/issues/88

Please check all that apply for this PR:

• [ ] introduces a new task
• [x] changes an existing task
• [ ] changes the Dockerfile
• [ ] introduces a breaking change (other users will need to make manual changes when this is released)

Did you update the README as appropriate for this change?

• [ ] YES
• [x] N/A

How should this change be described in release notes?

The bbl-up and bbl-destroy tasks can now create tarballs from the bbl-state directory instead of attempting to commit them to a git repository. This allows the tarball to be uploaded to S3 or GCS by a subsequent put step. This is controlled by an optional STORE_BBL_STATE_AS_TARBALL parameter.

What is the level of urgency for publishing this change?

• [ ] Urgent - unblocks current or future work
• [x] Slightly Less than Urgent

Tag your pair, your PM, and/or team!

[cfdreddbot]

:white_check_mark: Hey davewalter! The commit authors and yourself have already signed the CLA.

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/166704993

The labels on this github issue will be updated when the story is started.