Don't call fsync in end-to-end test

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Make prune-packed remove redundant pack files

Previously, ca-cas-prune-packed would only remove redundant unpacked objects,
but this patch extends it to also remove unneeded pack files.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>