`synchdb_add_olr_conninfo` not check if connection exists

[hanjianqiao]

postgres=# SELECT synchdb_add_olr_conninfo('olrconn',
                                'OpenLogReplicator',
                                7070,
                                'ORACLE');
 synchdb_add_olr_conninfo 
--------------------------
                        0
(1 row)
postgres=# select * from synchdb_attribute ;
 name | type | attrelid | attnum | ext_tbname | ext_attname | ext_atttypename 
------+------+----------+--------+------------+-------------+-----------------
(0 rows)