Convert remaining callers of lookup_blob to object_id

Convert remaining callers of lookup_blob to object_id

All but a few callers of lookup_blob have been converted to struct
object_id.  Introduce a temporary, which will be removed later, into
parse_object to ease the transition, and convert the remaining callers
so that we can update lookup_blob to take struct object_id *.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>