Add integration test for manifet diff.
Add integration test for manifet diff.

[delivers #173478943]

Co-authored-by: Jenna Goldstrich <ece644b3066e86d728b815a5811e74b079a9aacc@pivotal.io>
Co-authored-by: Teal Stannard <1a88a6ba53aca246419a6adc58411b995735316a@pivotal.io>

cloudfoundry/cli,cloudfoundry/cli,cloudfoundry/cli