It is necessary to copy pilot IDs of existing results to a temporary table
before fetching undone jobs from the DB: Otherwise, due to MyISAMs
table-level locking, collect_result_thread() will block in INSERT (SHOW
PROCESSLIST state "Waiting for table level lock") until the (streamed)
pilot query finishes. As one pilot query follows after the other,
collect_result_thread() may even starve until the memory for the
JobServer's "done" queue runs out, resulting in a crash and the loss of all
queued results.
Change-Id: Ib0ec5fa84db466844b1e9aa0e94142b4d336b022
25a390970a