Send build info as WORK_DATA.

Send a WORK_DATA packet as soon as the build starts as well as
immediately after it terminates (and before the WORK_FAIL/SUCCESS)
packet with build information such as name, number, url, status,
etc.

Remove the textual build result descriptions -- the client can
refer to the most recent WORK_DATA packet for information.

Don't send parameters back; the client probably already knows them.

Change-Id: I7432cd73951a91afe428994c7b8222c63fb0eab8