Consolidate http clients for uploading and polling
Consolidate http clients for uploading and polling

- We're no longer using cfhttp which is a thin wrapper around the
  default Golang HTTP client as it didn't seem to provide much value for
  our use case

[#139996781]

Signed-off-by: Sandy Cash <2b9a2783f4310a0eb3d7a964ff1c01a566f9acfe@gmail.com>

cloudfoundry-incubator/cc-uploader