use dropsonde for logging

Note: this change requires an update to cf-release to add the new, simplified loggregator property. We have made this change and it's making its way through our pipeline: https://github.com/cloudfoundry/cf-release/commit/069fe6eaa869cc911303bf95617b7d04ed862920
Please wait until the change is in cf-release/develop before merging this pull request and bumping it in cf-release.