Our CI jobs' logserver wasn't setting cache headers so browsers were
always downloading the log files on each request. Reduce load on the
logserver and improve performance by users via the setting of a 2 week
ttl on log data.
This should be safe because each job writes to a uuid identified dir and
that data doesn't get overwritten. Once written the data is static.
Change-Id: Ic99df4e4e64a6bf64e68e6f1bc297c91134ab716
23425ea940