Bump garden, gomega, cacheddownloader

[delivers #79624026] [delivers #79614122] [delivers #79467290]

Bump cloudfoundry-incubator/garden:
  Amit Gupta:
     Fix data race in client connection test ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/garden/builds/36726112 )
Bump Amit-PivotalLabs/gomega:
  Onsi Fakhouri:
     Merge pull request #65 from Amit-PivotalLabs/ccc
  Amit Gupta:
     Add CloseClientConnections function to ghttp
Bump pivotal-golang/cacheddownloader:
  Amit Gupta:
     Return ReadCloser for cached file when downloaded file is same as cache ( Travis Unknown )