Add check for Aiven API token in pipelines script
Add check for Aiven API token in pipelines script

This means that the pipeline will fail early if the API token hasn't
been uploaded, instead of waiting until the post-deploy task before
failing.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf