Backfill CHANGELOG.md for v6.17.0
Backfill CHANGELOG.md for v6.17.0

[ci skip]
Signed-off-by: Chris Hendrix <f9e38fc3e1ff46784bdcadbf77d17f93932faf2c@pivotal.io>

cloudfoundry/cli,cloudfoundry/cli,cloudfoundry/cli