get_ref_states: strdup entries and free util in stale list

get_ref_states: strdup entries and free util in stale list

The entries in states->stale list is filled in handle_one_branch() that is
a call-back funcation to for_each_ref() using the callback parameter given
to it.  We need to strdup() the refnames (both the string list key and the
value stored in util) for more permanent storage and free them when we are
done.

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>