Add api-availability-tests job to pipeline
Add api-availability-tests job to pipeline

We want the api-availability-tests job to start _before_ `cf deploy`
begins and end _after_ `cf deploy` ends.

Since this is very concoursey, the `pre-deploy` job will poll for the
existance of a file in the state bucket at
"jobs/$PIPELINE_VERSION/api-availability-tests" before continuing and
the api-availability-tests job will write out this file before running
the tests.

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