Re-adding get_site_job_data(): Now uses host platform for hostname.

Update to CL http://codereview.chromium.org/6677136/
 - Changing default keyval info with get_site_job_data() allows cleaner reporting and smaller tko_machines tables when multiple machines are used on the same job.

Now hostname will only be updated in multimachine jobs when the platform of a host can be retrieved from AFE.  The platform will be used as the hostname to prevent breaking the dashboard.

Change-Id: I24c6a6937b583ca3d10f5c9bfb759346ae6a2b26

BUG=None.
TEST=Tested multimachine BVT run in the lab.

Review URL: http://codereview.chromium.org/6805015
1 file changed