Fail Gcp4sLiveSuite early if no credentials

[valencik]

Previously if there was no SERVICE_ACCOUNT_CREDENTIALS environment variable the end-to-end tests would fail but only after munit timed out 30 seconds later.

This PR changes things to fail sooner and with a more direct error message:

gcp4s.bigquery.EndToEndSuite:                                                                                                                         
==> X gcp4s.bigquery.EndToEndSuite.projects contains project id  0.076s
  java.lang.Exception: Could not find 'SERVICE_ACCOUNT_CREDENTIALS' in ENV