Update nightly pipeline to run airgapped to run full suite

What does this MR do?

Updates the pipeline to run full suite against Airgapped instance rather than just smoke tests.
Part of Extend gitlab-qa Airgapped tests to run against... (gitlab-org/gitlab-qa#694 - closed)

Waiting for the following MRs before proceeding

• Extend airgap to use gitaly cluster for a broad... (gitlab-org/gitlab-qa!1092 - merged)
• Update GITLAB_QA_VERSION to 8.14.1 (!255 - merged)

Check-list

• Verify the change in all affected pipelines.
  • nightly