Fix reference to cnb build image in tests (should make this configurable from pipeline)
Fix reference to cnb build image in tests (should make this configurable from pipeline)

Co-authored-by: Daniel Thornton <5874b3971aa460e96f75d4dbef8f6aadb66f1697@pivotal.io>

cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack