contrib/lo: Add test for function lo_oid()

Author: Ronan Dunklau
Discussion: https://postgr.es/m/ZzMSJkiNZhimjXWx@paquier.xyz

Author: michaelpq

contrib/lo/expected/lo.out

@@ -47,4 +47,10 @@ SELECT lo_get(43214);
 DELETE FROM image;
 SELECT lo_get(43214);
 ERROR:  large object 43214 does not exist
+SELECT lo_oid(1::lo);
+ lo_oid 
+--------
+      1
+(1 row)
+
 DROP TABLE image;

contrib/lo/sql/lo.sql

@@ -27,4 +27,6 @@ DELETE FROM image;
 
 SELECT lo_get(43214);
 
+SELECT lo_oid(1::lo);
+
 DROP TABLE image;