pgsql-server: copy_relation_data was mistakenly assuming that the source

Log Message:
-----------
copy_relation_data was mistakenly assuming that the source relation
would always be already open at the smgr level. Per bug report from
Fabien Coelho.

Modified Files:
--------------
pgsql-server/src/backend/commands:
tablecmds.c (r1.129 -> r1.130)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/tablecmds.c.diff?r1=1.129&r2=1.130)