Add integration-linux-client-creds job to CI
Add integration-linux-client-creds job to CI

- This is to gain some confidence in our integration test changes
- We will revisit this later to run all the suites under client
  credentials
- Not yet blocking `create-installers` and `cats` on this job until we
  are comfortable that it is working correctly

[#166809126](https://www.pivotaltracker.com/story/show/166809126)

Co-authored-by: Andrew Crump <bad96bc28586e95c5d7da81c13d926ea5028b22f@pivotal.io>

cloudfoundry/cli,cloudfoundry/cli,cloudfoundry/cli