refs: convert reflog_expire parameter to struct object_id
reflog_expire already used struct object_id internally, but it did not
take it as a parameter. Adjust the parameter (and the callers) to pass
a pointer to struct object_id instead of a pointer to unsigned char.
Remove the temporary inserted earlier as it is no longer required.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>