Until osbuild-14, the images were unconditionally kept in the cache,
meaning the cache could grow very large. Now only the downloaded RPMs
are saved, which greatly limits how big it can grow.
Having the RPMs cached should speed up all but the first image build a
lot, so we should take advantage of that by not flushing the cache
between each build.
The cache is still flushed when the worker is stopped / restarted.
This moves the cache from /var/tmp/osbulid-worker* to
/var/cache/osbulid-worker/osbulid-worker-*. This means that each worker
gets a dedicated cache, in case there are several on one machine. In the
future we may want to combine them and only ever have one cache, but for
that we need improvements in parallel access and cache-cleanup.
Signed-off-by: Tom Gundersen <teg@jklm.no>
6002a128b8