Fix logical replication to fire BEFORE ROW DELETE triggers.

Before, that would fail to happen unless a BEFORE ROW UPDATE trigger
was also present.

Noted by me while reviewing a patch from Masahiko Sawada, who also
wrote this patch.  Reviewed by Petr Jelinek.

Discussion: http://postgr.es/m/CA+TgmobAZvCxduG8y_mQKBK7nz-vhbdLvjM354KEFozpuzMN5A@mail.gmail.com
