(2 of 2) Refactor and move Autotest downloader to the Dev Server.

Added two new Dev Server handlers:
1. Given GS url, download and install the build image.
2. Return the control file for a particular build.

BUG=chromium-os:22954
TEST=update_engine_client --update and gmerge.

Change-Id: Id383ca3aa3314d61a690b5278f190d492f98cd32
Reviewed-on: https://gerrit.chromium.org/gerrit/12803
Reviewed-by: David James <[email protected]>
Commit-Ready: Frank Farzan <[email protected]>
Tested-by: Frank Farzan <[email protected]>
1 file changed