send-pack: rename ref_update_to_be_sent to check_to_send_update
This renames ref_update_to_be_sent to check_to_send_update and inverts
the meaning of the return value. Having the return value inverted we
can have different values for the error codes. This is useful in a
later patch when we want to know if we hit the CHECK_REF_STATUS_REJECTED
case.
Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>