The linaro mirror node only has a 100GB cache volume to be shared
between OpenAFS and Apache. Each cache gets a ~50GB filesystem dedicated
to it. Unfortunately we were telling Apache's cache pruning system to
limit to 60000M which is large than 50GB. THis resulted in the cache
filling up and I think it may also be the source of errors.
Address this my reconfiguring htcacheclean to limit to ~40GB. This limit
is set with some buffer space as htcacheclean runs periodically and has
to keep things low enough to avoid filling up.
Change-Id: I7af3daa396b1631feefed5952460b8a9710b25b5
847a835d3a