Preparing to upstream: Created host_attributes and server_job_utils files.

Created a host_attributes file which by default doesn't do much on its own, but uses site_host_attributes when present to define attributes.  The existing HostAttributes class did not change so no existing use should regress.

Created a server_job_utils file to hold the helper classes test_item and machine_worker.  These classes are used by distribute_across_machines to manage tests and machines.

Change-Id: I4a5795bc7e6e865f616e4becf1e0781c1f51fe2b

BUG=none.
TEST=Run BVT with parallel_on_machines and distribute_across_machines on lab machines.

Review URL: http://codereview.chromium.org/6677157
3 files changed