Fix pg_control_checkpoint from commit 4b0d28de

Author: Simon Riggs <simon@2ndQuadrant.com>
Reported-By: Andreas Seltenreich <seltenreich@gmx.de>

src/backend/utils/misc/pg_controldata.c

@@ -90,7 +90,7 @@ pg_control_checkpoint(PG_FUNCTION_ARGS)
 	 * Construct a tuple descriptor for the result row.  This must match this
 	 * function's pg_proc entry!
 	 */
-	tupdesc = CreateTemplateTupleDesc(19, false);
+	tupdesc = CreateTemplateTupleDesc(18, false);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "checkpoint_lsn",
 					   LSNOID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "redo_lsn",