Bump src/loggregator

Bump :
  Jared Carroll:
     Support HTTPS for syslog drains
     SinkManager extraction and refactoring
     Extract SinkManager from MessageRouter
     update storeadapter
     Handle expired app services
     split store into a store and a watcher
  Dakota Bailey:
     Pass in url to SyslogWriter instead of scheme and host.
     Display app index in syslog messages
     update loggregator lib to latest
     remove unused function
     DumpSinks unregister after a period of inactivity.
  cf-lamb:
     Merge pull request #14 from james-masson/patch-1
  James Masson:
     Updated docs
  Alex Jackson:
     first cut at moving sinkserver tests to ginkgo
     more timing race fixes
     attempt to fix issues on travis
     move flaky tests to ginkgo
     reenable store tests
     fix hanging tests
     extract cache from app service store
     Dumping from a dump sink returns an array
     Ignore ginkgo
     bump storeadapter
     send both updates and removals from the app service store to the outgoing channels
     bump storeadapter
     remove debugging from travis script
     another attempt to get etcd to work on travis
     another attempt to get etcd to work on travis
     fix store reference to etcdstorerunner
     fix travis
     beginnings of the store backed by etcd
     fix paths in build script
     add etcd
  John Tuley:
     Go fmt
     Introduce Ginkgo specs
     Refactor HttpServer into WebSocketServer
     Mark app service store specs as pending
  Chris Wang:
     refactor tests to remove flakyness
     update loggregatorlib to latest
  Johannes Petzold:
     Drop messages when the message router channel is full, additional metrics.
     Bump loggregatorlib
     Immediately blacklist invalid syslog drain URLs
     [fixes #64068588] We need to ignore the four first control bytes when the stdout or stderr socket is opened
  Matthew McNew:
     Syslog sink discconnects to prevent hanging go routines
  Johannes Tuchscherer:
     close output channel in dumpReceiverChan if no dump for app exists [fixes #64099580]