taskd/clone.sh: clean up more crud on exceeds limit failures

taskd/clone.sh: clean up more crud on exceeds limit failures

Refactor part of the cleanup_failed_clone function into a new,
internal _cleanup_failed_clone_bloat function that can be reused
and which is responsible for removing any "crud" files that
might potentially use a non-trivial amount of space.

Call the new _cleanup_failed_clone_bloat from the cleanup_failed_clone
to make it retain exactly the same semantics as before.

Add a call to the new _cleanup_failed_clone_bloat function from the
clear_all_objects_and_packs function so that any exceeds-limit
clones immediately remove potentially bloating files at the same
time they remove their objects and refs.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>