Fix bug with view locking code.

LockViewRecurese() obtains view relation using heap_open() and passes
it to get_view_query() to get view info. It immediately closes the
relation then uses the returned view info by calling
LockViewRecurse_walker().  Since get_view_query() returns a pointer
within the relcache, the relcache should be kept until
LockViewRecurse_walker() returns. Otherwise the relation could point
to a garbage memory area.

Fix is moving the heap_close() call after LockViewRecurse_walker().

Problem reported by Tom Lane (buildfarm is unhappy, especially prion
since it enables -DRELCACHE_FORCE_RELEASE cpp flag), fix by me.

src/backend/commands/lockcmds.c

@@ -263,7 +263,6 @@ LockViewRecurse(Oid reloid, Oid root_reloid, LOCKMODE lockmode, bool nowait)
 
 	view = heap_open(reloid, NoLock);
 	viewquery = get_view_query(view);
-	heap_close(view, NoLock);
 
 	context.root_reloid = root_reloid;
 	context.lockmode = lockmode;
@@ -272,6 +271,8 @@ LockViewRecurse(Oid reloid, Oid root_reloid, LOCKMODE lockmode, bool nowait)
 	context.viewoid = reloid;
 
 	LockViewRecurse_walker((Node *) viewquery, &context);
+
+	heap_close(view, NoLock);
 }
 
 /*